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Task ID: 000491
Gypsum, or calcium sulfate hemihydrate obtained by heating calcium sulfate dihydrate at 130,0*C in furnaces. Determine the mass of calcium sulphate dihydrate which must be heated in a kiln in order to form 400,0 kg of plaster of paris.
Task ID: 001227
A mixture of lithium and sodium hydrides reacted with 193 cm3 of water. The weight of the solution obtained by 1 gram is less than the sum of the masses of all starting materials, and the mass fraction in the percentage of alkalis in the solution amounted to 8%. Determine the mass of the source hydrides.
Task ID: 001231
A mixture of potassium superoxide and sodium peroxide weighing 47.2 g was dissolved in water. This yielded 10.8 liters (0*C, 101325 Pa) of gas. Calculate the masses of the substances in the initial mixture.
Task ID: 001233
How many grams of a mixture of potassium and sodium must be dissolved in water so that the gas formed will occupy a volume of 7,392 liters (0*C, 101325 Pa) if the composition of the mixture contains 58.5% (by mass).
Task ID: 001236
Divalent metal hydride was dissolved in 841.5 g of water. The dissolution resulted in 4.48 liters (0*C, 101325 Pa) of gas and a solution with a concentration of 2%. The hydride of which metal was dissolved in water?
Task ID: 001237
A mixture of sodium bicarbonate and sodium carbonate with an amount of substances of 0.8 mol was treated with 117.6 grams of 50% sulfuric acid solution until complete neutralization. Calculate the mass fraction of the reaction product (in percent).
Task ID: 001238
To the hydrochloric acid and aluminum chloride volume of 500 ml, was added 2 molar solution of ammonium hydroxide 750 ml. The reaction was completed by the formation of a precipitate. The solution was evaporated and roast to a constant weight of 20.4 g. Calculate the amount of substances of the initial mixture.
Task ID: 001239
32 g of copper was dissolved in concentrated sulfuric acid and then in nitric acid. The obtained copper salts were roast to constant mass at a temperature of 200*C, and obtained a solid residue mass of 56 g. Determine how many moles of each of the acids were spent to dissolve the copper.
Task ID: 001241
We have two cells with inert electrodes. Cell 1 contains a solution of cuprum (II) sulfate with an amount of substance of 2 mol. The cell 2 contains a solution of cuprum (II) sulfate with a substance amount of 3 mol. Through the cells connected in series, they passed a current of 6F (Faraday). Calculate the mass of substance that will be released on the cathodes of each cell.
Task ID: 001242
A mixture of ethene and ethine 26.88 liters (0*C, 101325 Pa) was burned. In this case, 1640 kJ of heat was released. Calculate the volume ratio of each of the gases in the initial mixture based on thermochemical equations of chemical reactions: С2Н2 + 2,5О2 = 2СО2 + Н2О + 1300 kJ; С2Н4 + 3О2 = 2СО2 + 2Н2О + 1400 kJ.
Task ID: 001243
Silver was dissolved in 100 g of 70% nitric acid solution. The mass fraction of nitric acid after the reaction is 40%. To the resulting solution was added the same mass of 10.4% sodium chloride solution. Determine which substances and in what percentage concentration remained in solution.
Task ID: 001244
Electrolysis of a mixture of Cu(NO3)2 and AgNO3 solutions with a total volume of 400 ml. The amount of electricity passed through the solutions is 3860 C, with two metals totaling 2.80 g at the cathode. Calculate the molar concentration of salts in the initial mixture.
Task ID: 001245
Through a mixture of 0.2 M AuCl3 solution and 0.3 M CuCl2 solution, a current of 8A of 965 s (inert electrodes) was passed. The volume of solution in excess. Determine the gas that was released at the anode and calculate the volume of gas in milliliters (0*C, 101325 Pa).
Task ID: 001248
112 l (0*C, 101325 Pa) of a mixture of ozone and nitrogen was passed through an excess amount of potassium iodide solution. The mass of the gas mixture has decreased by 48 g. Calculate the volume fraction of ozone in the initial gas mixture.
Task ID: 001256
Based on the values of the oxidation of the atoms of the corresponding chemical elements, provide a reasoned answer to the question: which of the two hydroxides is the stronger basis? CuOH or Cu(OH)2; Fe(OH)2 or Fe(OH)3; Sn(OH)2 or Sn(OH)4. Write the equations for the chemical reactions that prove the amphoteric state (II) of the hydroxide.
Task ID: 001259
Using the values of standard enthalpy and absolute standard entropy of the corresponding substances, calculate the standard Gibbs energy of the reaction proceeding by the equation: C2H6 (g) = C2H4 (g) + H2 (g) Can this reaction occur under standard conditions?
Task ID: 001260
Ammonium nitrate is decomposed in two ways according to the following chemical reaction equations: 1. NH4NO3 (k) = N2O (g) + 2H2O (g); 2. NH4NO3 (k) = N2 (g) + 1/2O2 (g) + 2H2O (g). Which of the following reactions is more probable and which is more exothermic at 25*C? How will the likelihood of temperature reactions change?
Task ID: 001262
Calculate the mass of plumbum (II) sulfate resulting from the interaction of 150 g. 8% solution of plumbum (II) nitrate with 70 g. 6% sodium sulfide, followed by the interaction of the precipitate with excess dilute nitric acid.
Task ID: 001264
The graphite was treated with concentrated nitric acid when heated. The resulting gas mixture was passed through a saturated solution of calcium hydroxide. Make a reaction equation. Specify what is formed by the interaction of: a) graphite with concentrated sulfuric acid; b) steam with coke.
Task ID: 001265
860 ml of hydrogen gas mixture was unreacted. The gas mixture obtained after the reaction was passed through an ammonia solution, reducing the gas volume by 580 ml. Calculate the volume fraction of each gas in the initial mixture.
Task ID: 001266
In the homogeneous gas system A + B = C + D the equilibrium was established at the following concentrations: [B] = 0.05 mol/l; [C] = 0.02 mol/L. The equilibrium constant of the gas system is 0.04. Calculate the initial concentrations of substances A and B.
Task ID: 001270
In the process of electrolysis of a solution of cadmium salt 3434 Kl (Pendant) of electricity was consumed and 2.00 g of cadmium was obtained. Calculate the molar mass of cadmium equivalent.
Task ID: 001271
One iron product was coated with nickel, the other tin. Which coating will be anodic, which will be cathodic, and why? Make the electronic equations of the anode and cathodic corrosion processes of this product when the integrity of the coating in an acidic environment is impaired. In which case will the corrosion proceed more actively?
Task ID: 001272
When nitric acid is added to a solution of argentum (I) diamino chloride [Ag(NH3)2]Cl, a precipitate of argentum (I) chloride is formed. Write the molecular and ionic molecular equation for the reaction, explain the reason for the destruction of the complex ion.
Task ID: 001277
Write the equation of the equilibrium constant for the reaction: 2CO (g) = C (s) + CO2 (g). Answer the Question: If you reduce the pressure in the system, what happens with the following indicators a). The reaction rates v1: v2; b). The rate constant (Arrhenius equation); in). Equilibrium constant; d). The ratio of reaction rates v1: v2; e). Which way will the balance shift?
Task ID: 001280
The isoelectric point of albumin is pI = 4.75. In what ratio is it necessary to take normal concentrations of salt and acid in acetate buffer so that the protein has a neutral charge? (Kdis. (CH3COOH) = 1.78*10^-5).
Task ID: 001281
A mixture of 40 g of phenol and ethyl ester of monobasic carboxylic acid reacts with 65.5 ml of a 20% solution of sodium hydroxide (p = 1.22 g/cm3). When treating the same amount of the mixture, excess bromine water dropped 33.1 g of sediment. Define the ether structural formula?
Task ID: 001282
5 ml of a 1.3M solution of Na2SO4 (p = 1.150 g/cm3) was diluted to 100 ml. calculate the mass fraction and the molar concentration of the equivalent solution obtained if p = 1,0065 g/cm3.
Task ID: 001283
Draw up the coordination formulas of the seven complex compounds that can be obtained using Co3+, NH3, NO2-, K+ particles. Write their dissociation equation in aqueous solutions. The Co3 + coordination number is 6. Write the chemical reaction equation: NH4 + K3[Fe(CN)6] = N2 +…
Task ID: 001284
The carbon (IV) oxide obtained from the combustion of methane obtained from 56 m3 (0*C, 101325 Pa) of natural gas was passed through a solution of barium hydroxide. What is the amount of sediment formed if the methane content of natural gas is 80%?
Task ID: 001289
The content of toxic carbon (II) oxide in the exhaust gas can be reduced as a result of oxidation to oxygen (IV) of the oxide by oxygen: 2CO + O2 = 2CO2. How will the reaction rate change if the total system pressure is increased 4 times?
Task ID: 001291
What is the mass of HNO3 contained in 1 liter of 2M solution?
Task ID: 001292
On some expensive cars, prestigious brands of the car body, for the purpose of corrosion protection, is covered with a layer of tin. Will iron corrosion break when such a coating is scratched? Show a diagram of a galvanic element that occurs when the integrity of the tin coating is broken in an acidic environment. Calculate EMF for standard conditions.
Task ID: 001294
The motorist, having removed the rechargeable battery, left the copper battery terminals on the unpainted surface of the steel body. What process will occur in humid air? What kind of metal will be destroyed? Draw a diagram of a galvanic element and calculate the EMF for it under standard conditions.
Task ID: 001299
The solubility of the salt at 90*C and 25*C is 42.7 g/l and 6.9 g/l, respectively. What mass of water and salt should be taken to prepare the solution if 200 g of salt were crystallized during cooling from 90*C to 25*C?
Task ID: 001301
The 10 g silver coin had the word PURE SILVER. 0.3000 g of coins were taken for analysis, dissolved in nitric acid and precipitated from the resulting solution of argent in the form of AgCl. After washing and drying, the precipitate mass was 0.1990 g. How many percent of silver (by mass) is actually contained in the coin?
Task ID: 001302
When treated with a solution of sodium hydroxide 3.90 g of a mixture of aluminum with aluminum oxide emitted 840 ml of gas (0*C, 101325 Pa). Calculate the percentage composition (by mass) of the original mixture.
Task ID: 001307
Berlethol salt (potassium chlorate) decomposes to form KCl and O2 when heated. How many liters of oxygen can be obtained from 1 mole of KClO3 if the volume is measured at 0*C and 101.3 kPa?
Task ID: 001311
To 300 ml of Na2CO3 solution (ω = 18% ρ = 1.19 g/cm3) was added 500 ml H2SO4 solution (ω = 6% ρ = 1.04 g/cm3) which volume of 2.5 n HCl solution is required to interact with Na2CO3 residue?
Task ID: 001312
Name the complex compounds, calculate the oxidation state of the complexing agent, the coordination number of the complexing agent and the oxidation state of the complex ion; specify the ligands and write the equation of the instability constant: [Co(H2O)(NH3)2(CN)]Br2; [Cr(H2O)3(C2O4)Cl]; (NH4)[Hg(SCN)4]; [Pd(NH3)3Cl]2[P3Cl4].
Task ID: 001315
Based on the structure of the hydrogen atom: a) indicate the possible valence states and oxidation states of the hydrogen; b) describe the structure of the H2 molecule from the standpoint of the EO (valence bond method) and MO (molecular orbital method); c) justify the impossibility of the formation of the molecule H3.
Task ID: 001318
To a solution containing 0.20 mol of FeCl3 was added 0.24 mol of NaOH. How many moles of Fe(OH)3 were formed as a result of the reaction and how many moles of FeCl3 remained in solution?
Task ID: 001321
Why, when producing carbon (IV) oxide from marble, is marble affected by hydrochloric acid rather than sulfuric acid? What is the volume (CO2) of CO2 obtained from 1 kg of marble containing 96% CaCO3?
Task ID: 001325
The Ksp of CuCO3 at 25*C is 2.36*10^-10. Calculate the concentration of Cu2+ ions in a saturated CuCO3 solution containing K2CO3 in the amount of 0.001 mol/l, the degree of K2CO3 dissociation is equal to 95%.
Task ID: 001326
What volume of potassium hydroxide solution with w = 30% and p = 1286 kg/m3 should be taken in order to get 2*10^-4 m3 of solution from KOH with w = 10% and p = 1082 kg/m3 w = 20% and p = 1176 kg/m3? (Solving with a mathematical equation).
Task ID: 001328
Will precipitate CdCO3, if up to 2 liters. 0.05M K2[Cd(CN)4] solution containing 0.06M KCN excess, add 1 liter. 0.03 M K2CO3 solution? K([Cd(CN)4]2-] = 7.66*10^-18; Ksp(CdCO3) = 2.50*10^-14.
Task ID: 001330
5.1 g of powder, partially oxidized magnesium was treated with hydrochloric acid. As a result of the chemical reaction stood out 3.74 l. H2, (0*C, 101325 Pa) How much percent of metallic magnesium was contained in the sample?
Task ID: 001332
What is the volume of hydrogen measured at a temperature of 25*C and a pressure of 755 mm. Hg Art. (100.7 kPa), is released by the interaction of 1 g of an alloy consisting of 30% potassium and 70% sodium.
Task ID: 001333
To find the order and the rate constant of the reaction method of the Substitution and the Vant-Goff method, flowing at a temperature of 398,2K using the data on the course of the reaction in time t (from the beginning of the reaction). N2O5 = N2O4 + 1/2O2.
Task ID: 001334
Draw a diagram of two galvanic elements, one of which is an aluminum cathode and the other anode. Write the equations for the reactions that occur when these galvanic elements work and calculate the standard EMF value?
Task ID: 001335
To 160 kg of 10% solution of cuprum (II) sulfate was added 12 kg of iron sawdust. What amount of copper will be released if the yield of the product is 90% of the theoretical possible?
Task ID: 001345
100 ml of solution contains 200 mg of Ba2+ ions and 1 mg of Pb2+. Which substance will precipitate first and foremost with a gradual increase in K2CrO4 concentration? Is it possible to quantify these cations in this solution using potassium chromate?
Task ID: 001350
What is reproducibility in chemical analysis? What criteria do you use to evaluate reproducibility? Define the concept of deviation, mean deviation, range of variation, variance, standard deviation.
Task ID: 001361
Scheme two galvanic elements, one of which is iron is the cathode and magnesium is the anode. Select the second electrode yourself. For one of the galvanic elements, write the equation of electrode processes and current-forming reactions, calculate the standard EMF of the galvanic element using: a) standard electrode potentials; b) the change in Gibbs standard energy in the current-forming reaction.
Task ID: 001362
What process, oxidation, or reduction occurs in the transformed conditions? Based on the data of the table “Standard electrode potentials of redox systems”, calculate which substances: PbO2, I2, FeCl3, KMnO4 – can be used to perform the conversion of H2S → S.
Task ID: 001363
Calculate the potential of a metal electrode with the specified concentration of metal ions and the potential of a hydrogen (hydrogen) electrode with the specified concentration of hydrogen ions in solution. Draw a diagram of the galvanic element formed by these electrodes, write the equation of electrode processes and current-forming reactions. Calculate the EMF of the galvanic element. [Al3+] = 0.001 mol/l, [H+] = 10^-11 mol/l.
Task ID: 001364
Calculate the rigidity of the water in which 1 liter contains the mass of salts specified in the condition. Calculate the mass of sodium carbonate to be added to 150 liters of water to remove this stiffness. The composition of the solution: 111 mg CaCl2, 180 mg MgSO4, 2 mmol NaSO4.
Task ID: 001365
The water hardness, which is calculated only by calcium salts, is equal to T0. After boiling, the water hardness was 2.3 mmol/l. Why has the water hardness changed? Compile the appropriate reaction equation and calculate the mass of sediment formed from V l of water. The values of these variables are: T0 = 6.7 mmol/l, V = 25 l.
Task ID: 001367
Justify the calculations why Fe is corroded in solution with pH = 8.5 only in the presence of oxygen, and in non-oxygen solution – no? Draw a diagram of the galvanic element that occurs during the corrosion process and write the equation for the electrode process.
Task ID: 001368
Name the metal that can be used as: a) anode; b) cathode coating to protect chromium from corrosion. Draw up diagrams of the galvanic elements that are formed during atmospheric corrosion as a result of the disturbance of each coating, and write the equation of the electrode processes.
Task ID: 001369
Draw up the equation of the processes occurring on graphite electrodes during the electrolysis of an aqueous solution of salts Cu(NO3)2, NaBr, Ca(NO3)2. In which case only water is involved in the electrode processes? Calculate the masses of substances that are thus formed on the cathode and on the anode if the amount of electricity passed through the solution of these salts is 193000 A*s.
Task ID: 001370
Based on the degree of oxidation of the isolated chemical elements (square brackets), H[Cl]O and H2[S]; [Cl]2 and [F]2; H2[S]O4 and H[Cl]O4, and their location in the batch system, calculate whether redox reactions are possible between these compounds? Specify in the chemical formulas of the interacting compounds the oxidizing agent and the reducing atom.
Task ID: 001371
Using the electronegativity value of the elements, specify the direction of displacement of the total electron pair when bonding in the Al4C3, CO2, CF4 molecules. Specify the formula for the substance with the most polar chemical bonds.
Task ID: 001372
Make electronic formulas of atoms and present schemes of overlapping of atomic orbitals in HF, H2Te, SiH4 molecules. Draw conclusions about the geometric shape and polarity of each molecule.
Task ID: 001376
Draw up a scheme of electrolysis of an aqueous solution of Sn(NO3)2 with graphite electrodes. Write the electronic equations for the anode and cathode processes. Calculate the mass of substance released on the cathode if the electrolysis time is 35 min. at a current of 35 A.
Task ID: 001391
The rate of decomposition rate of nitrogen (V) of the oxide at 55*C by the reaction: 2N2O5 = 4NO2 + O2 is 1.7*10^-3. 5 liter capacity added 2 mol of nitrogen (V) oxide. Calculate the rate of reaction at the moment when in the reaction mixture: a). 0.1 mol of oxygen is formed; b). 0.1 mol of nitrogen (IV) oxide is formed; c). will remain 0.1 mol of nitrogen (V) oxide?
Task ID: 001392
The closed volume undergoes a chemical reaction: AB (gas) = A (gas) + B (gas). The equilibrium constant of the reaction is 0.4. The equilibrium concentration of substance B is 0.9 mol/l. Calculate: a). The initial concentration of the substance AB; b). How many percent of the substance AB has decomposed?
Task ID: 001393
Calculate the enthalpy of sodium sulfate hydration if the enthalpy of dissolution of the anhydrous salt of Na2SO4 (crystal) = -2.3 kJ/mol, the enthalpy of dissolution of the crystalline hydrate Na2SO4*10H20 = 78.6 kJ/mol.
Task ID: 001395
To prevent freezing in the winter, glycerol is added to the aqueous solutions. Assuming that Raoul’s law can be applied to similar solutions, calculate how many grams of glycerol should be added to 100 grams of water to freeze the solution to -5 degrees Celsius.
Task ID: 001396
Sodium carbonate was added to a saturated calcium carbonate solution to a concentration of Cm (Na2CO3) = 0.1 mol/l. Calculate the mass of CaCO3 in 2.5 l of saturated solution. How will the solubility of CaCO3 in the presence of Na2CO3 change?
Task ID: 001397
Explain the following observations. To the solutions containing the [Ag(NH3)2] and [Ag(CN)2] ions separately, H2S was added and the black Ag2S precipitate formed; add KI and observe the formation of a precipitate of yellow AgI in only one case; no sludge formation occurs when NaCl is added. Write the reaction equation and give reasonable explanations for the observed phenomena.
Task ID: 001399
The interaction of water vapor with hot coal produces water gas consisting of equal volumes of CO and H2. What volume of water gas (0*C, 101325 Pa) can be obtained from 3.0 kg of coal?
Task ID: 001401
Under the condition of phase equilibrium (ΔG = 0), calculate the entropy change in the evaporation of water in the amount of 3 mol at 100*C, if the heat of evaporation of water at this temperature is 2451 J/mol.
Task ID: 001402
Initial concentration of HCl, O2, Cl2 involved in the reaction: 4HCl (gas) + O2 (gas) = 2Cl (gas) + H2O (gas); respectively: 4.2; 1.8; 0.01 mol/l. Calculate the concentration of all the reactants after the oxygen concentration decreases to 1 mol/l. What mass fraction of each of the starting materials will react at that moment?
Task ID: 001408
Write down the equation of the rate of direct and reverse reaction, using concentrations, and the equilibrium constant of the chemical reaction system: C2H2 (gas) = 2C (solid) + H2 (gas)? H < 0. Where will the equilibrium shift when: a). Fever; b). Pressure reduction; c). Increased H2 concentrations?
Task ID: 001414
Water contains cations and anions at the following concentrations: [Mg2+] = 2.0 meq/l; [Ca2+] = 1.5 meq/l; [Na+] = 0.8 mEq/l; [Cl-] = 2.3 meq/l; [HCO3-] = 1.9 mEq/l; [SO4^2-] = 0.1 mEq/l. Calculate the total, temporary, and constant water hardness values.
Task ID: 001417
Derive, through concentration, the rate of the forward and reverse reactions, the equilibrium constant of the system: 2SO3 (liquid) = 2SO2 (gas) + O2 (gas) ∆H> 0. Where will the equilibrium shift when: a). Fever; b). Pressure reduction; c). Increased O2 concentrations?
Task ID: 001424
Calculate the mass of magnesium contained in a 100.0 ml volumetric flask if 14.31 ml of 0.04902 M EDTA solution were taken to titrate 10.00 ml of the magnesium salt solution selected from this flask.
Task ID: 001425
Calculate the masses of magnesium and calcium contained in 100.00 ml of a solution of the salts of these metals, if 20.28 ml is consumed when titrating 10.00 ml of this solution with 0.05000 M EDTA solution with the eryochrome black T indicator in the presence of ammonia buffer solution. EDTA solution, and titrated with murexide after adding 2 N. sodium hydroxide solution went to 12.89 ml EDTA solution of the same concentration.
Task ID: 001426
Calculate the molar concentration of the equivalent (normality) of sodium hydroxide solution if titration of 10.00 ml is 0.1115 N. hydrochloric acid solution consumed 9.89 ml of this solution.
Task ID: 001427
Calculate the pH of the start and end of the titration jump, excluding dilution of the titration solution, 100.00 ml 0.10 N. acetic acid solution of 0.10 N. potassium hydroxide solution.
Task ID: 001428
Calculate the equilibrium concentration of the hydrogen cations at the equivalence point, taking into account the dilution of the solution with a titration of 5.00 ml of 0.25 N. hydrazine solution of 0.25 N. hydrochloric acid solution.
Task ID: 001429
Calculate the mass of ferrum (II) contained in a 100.0 ml volumetric flask if 13.45 ml of 0.02089 N. was taken to titrate 10.00 ml of the Mor salt solution. potassium dichromate solution.
Task ID: 001430
Butadiene-1,3 by the method of SV Lebedev is obtained by passing the ethyl alcohol vapor over the catalyst at 450*C. The process is accompanied by the simultaneous dehydration and dehydration of alcohol. Calculate the volume of ethyl alcohol (ρ = 0.8 g/cm3) required to produce 120 liters of butadiene-1.3 (bp). The volume fraction of butadiene-1,3 is 75%.
Task ID: 001431
The mixture consists of CH4, C2H6, and CO, 15.68 liters (0*C, 101325 Pa) burned. This formed 48.4 g of CO2 and 28.8 g of H2O. Calculate the molar ratios of the gases in the initial mixture.
Task ID: 001432
A mixture of hydrogen and carbon monoxide with a volume of 100 ml was blown up with 80 ml of oxygen. After the explosion, the temperature of the system was lowered to that of the starting materials, with a volume of 130 ml. After condensation of water vapor the volume was reduced to 100 ml. Calculate the volume fraction of each of the gases of the initial mixture.
Task ID: 001433
A mixture of methylamine, ethylamine and methane volume of 17.99 liters (0*C, 101325 Pa) was burned. This produced 6.72 liters of nitrogen and 22.4 liters of carbon dioxide. Calculate the volume fraction of methylamine in the original mixture.
Task ID: 001434
The relative density of the mixture of formaldehyde and hydrogen with respect to helium is 6.1. A mixture of formaldehyde and hydrogen was heated over a nickel catalyst. In this case, all the hydrogen reacted. Calculate the relative density of the resulting gases with respect to air.
Task ID: 001435
The products formed by the combustion of a mixture of methane and ethane with a volume of 8.96 liters (0*C, 101325 Pa) (ρ = 0.87 g./l) were passed through a 17% solution of potassium hydroxide, weighing 200 g. To calculate the final reaction products and their mass.
Task ID: 001436
A mixture of propane, propene and ethane (0*C, 101325 Pa) was treated with 48 g of bromine. The relative density of the mixture with respect to hydrogen is 17.5. Calculate the volume fraction of each gas in the mixture.
Task ID: 001437
A mixture of H2S, SO3, CH4 gases was passed through a concentrated potassium hydroxide solution. As a result, the mass of the gas mixture decreased by 20 g. Calculate the volume in l (0*C, 101325 Pa) of sulfur (VI) oxide in the initial mixture.
Task ID: 001439
After combustion of a mixture of ethane and methylamine with sufficient oxygen, the water vapor was condensed and the volume of the remaining gases was 19.04 l (0*C, 101325 Pa). Then, the gas mixture was passed through an alkaline solution and the volume was 3.36 l (0*C, 101325 Pa). Calculate the mass of the original mixture.
Task ID: 001442
To neutralize 3.8 kg of a solution consisting of NaCl and HCl, 568 ml of 5.2 M sodium hydroxide solution were consumed. For complete precipitation of chlorine ions in the resulting solution, requires 4.37 l of 0.8 M AgNO3 solution. Calculate the amount of substances in the initial mixture.
Task ID: 001443
Calculate the number of hydrogen atoms replaced by chlorine during chlorination in the presence of light, 25.4 l (0*C, 101325 Pa) of ethane, if 1120 g of 20% KOH solution have been consumed to neutralize the HCl formed during the chemical reaction.
Task ID: 001450
Draw up an electrolysis scheme of an aqueous solution of Sn(NO3)2 with carbon electrodes. Write the electronic equations for the anode and cathode processes. Calculate the mass of substance released on the cathode if the electrolysis time is 10 min. Current 10A.
Task ID: 001454
Assemble the electroplating element using a tin electrode as the cathode. Calculate the EMF if the concentration of metal ions in the anode and the cathode are 0.001 mol/l and 5 mol/l, respectively.
Task ID: 001455
When electrolysis of an aqueous solution of argentum nitrate with carbon electrodes, the mass of one of the electrodes increased by 5.39 g. What is the product, and in what amount, was formed on the other electrode? How much electricity was passed through the cell?
Task ID: 001456
During the electrolysis of an aqueous solution of aluminum chloride with inert electrodes, 8 g of substance were released on the cathode. What is this substance? What product and how much stood out on the anode?
Task ID: 001459
Sodium cyanide is used to extract silver and gold from natural ores. When using 0.2% NaCN solution. Calculate the mole fraction of NaCN and H2O in this solution. Calculate the amount of water and salts required to prepare 1 kg of such solution.
Task ID: 001460
The galvanic element is formed by aluminum and zinc immersed in a solution of their salts Al2(SO4)3 (C(Al3+) = 10^-3 mol/l) and ZnSO4 (C(Zn2+) = 1 mol/l). Draw a diagram of the electroplating element. How does the galvanic element work? Calculate his EMF.
Task ID: 001461
Make a diagram of corrosive galvanic vapor and indicate the direction of electron motion. Write the electronic equations of the anode and cathode processes, as well as the total equation of the electrochemical process that occurs during the electrochemical corrosion of metals. Tin is soldered to silver. Which of the metals will be corroded if this pair of metals gets into an alkaline environment?
Task ID: 001462
To a solution formed under the action of 35.7 ml of a solution of sulfuric acid (ω(H2SO4) = 39.2%, ρ(H2SO4) = 1.4 g/cm3) at 8.125 g of zinc, was added 75 g of a solution of barium sulfide (ω(BaS) = 33.8%), the resulting mixture was slightly heated to completion of the reaction. Calculate the mass fraction of substances contained in the solution after the reaction. (Olympiad level chemistry task)
Task ID: 001466
Give a comparative characteristic of sulfite, selenium and telluric acids according to the following characteristics: a) stability; b) acidic properties; c) redox properties. Give the answer with examples of appropriate chemical reactions.
Task ID: 001467
The oxidation of 16.73 g of divalent metal formed 21.54 g of its oxide. Calculate the molar masses of the metal equivalent and its oxide. Why is the molar and relative atomic mass of metal equal?
Task ID: 001468
Quantum numbers for electrons of the external energy level of atoms of some elements have the following values: n = 4; l = 0; ml = 0; ms = + -0.5. Write the electronic formulas of the atoms of these elements and calculate how many free 3d orbitals each contain.
Task ID: 001469
What is a covalent bond called polar? What is the quantitative measure of covalent bond polarity? Based on the electronegativity values of the atoms of the corresponding elements, calculate which of the bonds HCl, ICl, BrF is the most polar.
Task ID: 001470
Calculate the thermal effect of the reduction reaction of ferrous (II) oxide with hydrogen based on the following thermochemical equations: FeO (solid) + CO (gas) = Fe (solid) + CO2 (gas); ΔH = -13.18 kJ. CO (gas) + 0.5O2 (gas) = CO2 (gas); ΔH = -283.0 kJ. H2 (gas) + 0.5O2 (gas) = H2O (g); ΔH = -241.83 kJ.
Task ID: 001471
How can it be explained that under standard conditions the exothermic reaction H2 (gas) + CO2 (gas) = CO (gas) + H2O (liquid); H = -2,85 kJ, is it impossible? Knowing the thermal effect of the reaction and the absolute standard entropies of the corresponding substances, calculate the Gibbs free energy of this reaction.
Task ID: 001472
The reaction proceeds according to the equation H2 + I2 = 2HI. The rate constant of this reaction, at a certain temperature, is 0.16. Initial concentrations of reactants (mol/l): [H2] = 0.04; [I2] = 0.05. Calculate the natural rate of reaction and its rate at [H2] = 0.03 mol/l.
Task ID: 001473
To 3 l of 10% solution of HNO3 with a density of 1,054 g/cm3 was added 5 l of 2% solution of the same acid with a density of 1,009 g/cm3. Calculate the mass fraction and molar concentration of nitric acid in the resulting solution, whose volume is 8 liters.
Task ID: 001475
Draw a diagram, write the electronic equations for the electrode processes and calculate the EMF of a galvanic element consisting of plates of cadmium and magnesium immersed in solutions of their salts at a concentration of [Mg2+] = [Cd2+] = 1 mol/l. Will the EMF value change if the concentration of each ion is reduced to 0.01 mol/l?
Task ID: 001476
If you drop the iron plate into the dilute sulfuric acid, the evolution of hydrogen is slow. However, if the zinc stick touches the iron plate, the rapid release of hydrogen begins. Why? What metal does it dissolve? Make the electronic equations of the anode and cathode processes.
Task ID: 001477
The instability constants of the complex ions of [Co(NH3)6]3+, [Fe(CN)6]4-, [Fe(CN)6]3- are respectively 6.2*10^-36, 1.0*10^-37, 1.0*10^-44. Which of these ions is more stable? Write the expression for the instability constants of the complex ions indicated and the formula of the compound containing these ions.
Task ID: 001479
Write the formulas and name the oxy-containing acids of chlorine, specify the degree of oxidation of chlorine in each of them. Which acid is the stronger oxidizing agent? Based on electronic equations, the reaction equation KI + NaOCl + H2SO4 = I2 + will finish…
Task ID: 001480
In the presence of moisture, oxygen and carbon (IV) oxide, the copper is covered with a green coating. What is the name and what chemical formula of the compound? What happens if it is affected by hydrochloric acid? Write the process chemical reaction equation.
Task ID: 001481
Which polymer, unsaturated hydrocarbon, is natural rubber? Write the structural formula of this hydrocarbon. What is the process of converting rubber to rubber? How does rubber and rubber differ in structure and properties?
Task ID: 001483
How will the electrolysis of the K2SO4 aqueous solution occur when using inert electrodes? Give the electrolyte dissociation equation and explain the possibility of the participation of each of the formed ions in the electrode reactions. Draw up the electronic equations of the processes taking place on the electrodes. Calculate mass (for solids and liquids) or volume b.w. (for gaseous) substances formed on the electrodes. Electrolysis time is 2 hours; Current 15A.
Task ID: 001484
The water sample consists of H2O and D2O, with the mass fraction of oxygen atoms in the water sample being 88%. Find the mass fraction of heavy D2O water in the mixture (Olympics task).
Task ID: 001485
Using the background data, calculate the thermal effect of the Ca3(PO4)2 + 3SiO2 + 5C = 3CaSiO3 + 5CO + 2P reaction. Calculate how much heat you need to use to get 1 kg of yellow phosphorus.
Task ID: 001486
What is the maximum number of electrons (at the level and in the sublayer) that an atom can contain in the electron layer n = 4. What are the values of magnetic quantum numbers characteristic of these electrons?
Task ID: 001488
What is activation energy. Explain with an example.
Task ID: 001489
After mixing gases A and B in the system A + B = C + D equilibrium is established at the following concentrations: B = 0.5 mol/l, C = 0.2 mol/l. The equilibrium constant of the reaction is 4*10^-2. Find the initial concentrations of substance A and B.
Task ID: 001492
At a temperature of -5*C Gibbs energy of the transition of liquid water into ice is -68 J/mol. At + 5*C, this energy is +147 J/mol. In which case is the process H2O (liquid) = H2O (solid) arbitrary? At what temperature will the Gibbs energy of this transition be zero? (in two ways)
Task ID: 001497
Through a solution of FeCl2, a current of 3A duration of 10 minutes was passed, and through a solution of FeCl3 a current of 5A duration of 6 minutes was passed. In which case did more iron stand out?
Task ID: 001503
To make the ionic and molecular equations for the hydrolysis of salts of aluminum sulfate and sodium silicate. Note the reaction of the medium in the salt solution. Write the expression of the hydrolysis constant for these salts.
Task ID: 001505
Calculate the mass fraction of water in FeSO4*7H2O iron sulphate
Task ID: 001511
With the interaction of 3 g of saturated monohydric alcohol with excess sodium, 0.56 l (0*C, 101325 Pa) of hydrogen was released. Output the formula of the alcohol, write down the formulas of the possible isomers and name them.
Task ID: 001512
A portion of 0.6000 g of oxalic acid dihydrate was dissolved in a 100.0 ml volumetric flask. For titration of 20.0 ml of the resulting solution spent 18.34 ml of NaOH solution. Calculate the molar concentration of NaOH solution.
Task ID: 001513
In determining the iron in the wastewater sample volume of 200.0 ml, Fe2+ ions were oxidized to Fe3+, precipitated with ammonia, separated the precipitate from the solution and after dissolving the precipitate in hydrochloric acid, titrated 5.14 ml of 0.0050 M EDTA solution in the presence of sulfosalicylic acids. Calculate the total concentration of iron in water.
Task ID: 001514
A sample of 1.4790 g organic chloride was dissolved in a 250 ml volumetric flask. 25 ml of the resulting solution was treated with 50 ml of 0.1000M AgNO3 solution. 25.5 ml of 0.1000M NH4CNS solution was used to titrate the excess of the argument. Calculate the mass fraction of chlorine in the unknown chloride.
Task ID: 001515
Calculate the pH of 0.023 M hydrochloric acid solution.
Task ID: 001517
A current of 2 days was passed through a cell containing 10 l of 7.4% KOH solution (ρ = 1.06 g/cm3), after which the concentration of KOH in the solution was 8%. Calculate the current at which the electrolysis was carried out and draw up an electrolysis scheme for the KOH solution.
Task ID: 001519
Calculate the amount of heat released by the combustion of 20 liters (0*C, 101325 Pa) of diborane if ΔH(B2H5) = 31.4 kJ/mol and ΔH(B2O3) = -1264 kJ/mol? Is it advisable to use diborane instead of ethane as fuel if the standard ethanol combustion heat is -1559,88 kJ/mol?
Task ID: 001520
Will the equilibrium of the reverse reaction А + В = 2АВ be shifted, at a temperature decrease of 25 degrees, if the temperature coefficient of the direct reaction is 3.0 and the reverse reaction is 2.1?
Task ID: 001521
The rate constant of hydration of carbon (IV) oxide is 0.003; the rate constant of the proton transfer from the imidazole group is 1, (at t = 25*C). In what reaction will the half-transformation period be longer and how many times?
Task ID: 001525
Two zinc plates were placed in the hydrochloric acid solution, one of which was partially coated with nickel. In which case is the zinc corrosion process more intense? Motivate the answer by equating the corresponding processes.
Task ID: 001530
Substance A stored in the dark has no odor; however, when stored in light, it has a faint odor. When illuminated from A, a solid substance B and gas B is formed. Substance B is dissolved in a concentrated aqueous solution D, thus forming a solution D and gas E. Solution D again goes into solution D under the action of gas G with a sharp odor having acidic properties and formed by reaction of B with hydrogen. When mixing substance B with solution D, A is formed again, and when mixed with gas E and water, a solution containing G and Z is formed. Decipher substances A – Z and write the equation of all these reactions. (Olympics challenge)
Task ID: 001535
The starting mixture consists of 0.30 mol/l H2 and 0.20 mol/l N2. The system enters equilibrium when 0.24 mol/l H2 reacts. Calculate the equilibrium constant if the chemical reaction equation is 3H2 (gas) + N2 (gas) = 2NH3 (gas).
Task ID: 001538
The equilibrium constant of the chemical reaction I2 (gas) + H2 (gas) = 2HI (gas) at some temperature is 4. Calculate the equilibrium concentration of HI if the initial concentrations of H2 and I2 are respectively 0.030 and 0.012 mol/l.
Task ID: 001542
At a certain temperature, the equilibrium constant of the heterogeneous reaction FeO (solid) + CO (gas) = Fe (solid) + CO2 (gas) is equal to 0.5. What will be the equilibrium concentrations of CO and CO2 if their initial concentrations are: [CO] = 0.05 mol/l, [CO2] = 0.01 mol/l?
Task ID: 001545
The reaction proceeds according to the equation N2 + O2 = 2NO. The concentrations of the starting materials prior to the start of the reaction were [N2] ref. = 0.049 mol/l; [O2] ref. = 0.010 mol/L. Calculate the concentration of these substances at a time when [NO] equals = 0.005 mol/L.
Task ID: 001546
Calculate the change in internal energy of the reaction under standard conditions Na2CO3 (s) = Na2O (s) + CO2 (gas.). What amount of heat is required to decompose 10 kg of sodium carbonate?
Task ID: 001551
The reaction follows the equation H2 + I2 = 2HI. The rate constant of this reaction at some temperature is 0.16. Initial concentrations of reactants: [H2] = 0.04 mol/l; [I2] = 0.05 mol/l. Calculate the initial reaction rate and its rate when [H2] = 0.03 mol/l.
Task ID: 001552
The equilibrium constant of a homogeneous CO (gas) + H2O (gas) = CO2 (gas) + H2 (gas) system at some temperature is 1. Calculate the equilibrium concentrations of the reactants if the initial concentrations of [CO] are ref. = 0.01 mol/l; [H2O] ref. = 0.40 mol/l.
Task ID: 001555
The equilibrium constant of the homogeneous system N2 (gas) + 3H2 (gas) = NH3 (gas) at room temperature is 0.10. The equilibrium concentrations of hydrogen and ammonia are respectively 0.20 mol/l and 0.08 mol/l. Calculate the equilibrium and initial nitrogen concentration.
Task ID: 001559
At some temperature, the equilibrium of the homogeneous system 2NO (gas) + O2 (gas) = 2NO2 (gas) was established at the following concentrations of reactants: [NO] = 0.20 mol/l; [O2] = 0.10 mol/l; [NO2] = 0.10 mol/l. Calculate the equilibrium constant of this reaction and the initial concentrations of NO and O2.
Task ID: 001560
The equilibrium of the homogeneous system in the gas phase 4HCl + O2 = 2H2O + 2Cl2 was established at the following concentrations [H2O] = 0.14 mol/l; [Cl2] = 0.14 mol/l; [HCl] = 0.20 mol/l; [O2] = 0.32 mol/l. Calculate the initial concentrations of hydrogen chloride and oxygen.
Task ID: 001562
Oxidation of carbon and carbon (II) oxide proceeds by the equations: a). 2C + O2 = 2CO; b). 2CO + O2 = 2CO2. How will the speed of these reactions change if the volume of each system is reduced by 3 times?
Task ID: 001564
Write the mathematical expression of the equilibrium constant for the following reactions: a). N2 + 3H2 = 2 NH3; b). Fe2O3 + 3CO = 2Fe + 3CO2. How to increase the yield of reaction products? Both reactions are exothermic.
Task ID: 001577
For the following reversing process, write an expression of the equilibrium constant and calculate how the conditions of (C, P, T) can be changed so that the equilibrium shifts towards the formation of the reaction products: N2 + O2 = 2NO; ΔH = 180.8 kJ/mol.
Task ID: 001578
For the next reversal process, write an expression of the equilibrium constant and calculate how the reaction conditions (C, P, T) can be changed so that the equilibrium shifts toward the formation of the reaction products? 2CO + O2 = 2CO2
Task ID: 001579
The following substances were added to the FeCl3 solution: a). HCl; b). KOH; c). ZnCl2; d). Na2CO3. In which cases will hydrolysis of ferric (III) chloride increase? Why? Make the ionic and molecular equations for the hydrolysis of these salts.
Task ID: 001582
For the following reversal process, write an expression of the equilibrium constant and calculate how the conditions of the (C, P, T) change can be made to shift the equilibrium towards the formation of the reaction products (right): CaCO3 (s) = CaO (s) + CO2 ( gas); ΔH = 177.4 kJ.
Task ID: 001584
When transporting cargo from north to south, the temperature increased by 20*C. How to change the rate of possible chemical reactions? The temperature coefficient of reaction rate is 3.
Task ID: 001585
For the following reversal process, write an expression of the equilibrium constant and calculate how the conditions of (C, P, T) can be changed to shift the equilibrium to the right: CuO (s) + H2 (gas) = Cu (s) + H2O (gas) ; ΔH = -76.5 kJ.
Task ID: 001587
Calculate how the equilibrium of the system will change when the aggregate state of one of the products changes: CO2 (gas) + 4H2 (gas) = CH4 (gas) + 2H2O (gas); CO2 (gas) + 4H2 (gas) = CH4 (gas) + 2H2O (liquid) under standard conditions.
Task ID: 001591
Mathematics. Initial concepts.
Task ID: 001597
How many times will the reaction rate of 2A + B = 2C decrease when the pressure of all substances in the system is reduced by 3 times and the temperature is reduced by 30*C at the same time? The aggregate state is gas. The temperature coefficient of reaction rate is 2.
Task ID: 001598
A solution of sodium acetate in the presence of phenolphthalein is colorless. However, when heated, it becomes pink. Explain this phenomenon based on the total reactions occurring in sodium acetate solution.
Task ID: 001600
Oxidation of sulfur and sulfur (IV) oxide proceeds according to the equations: S (s) + O2 (gas) = SO2 (gas); 2SO2 (gas) + O2 (gas) = 2SO3 (gas). How will the speed of these reactions change if the volume of each system is reduced by 4 times?
Task ID: 001603
In a homogeneous system, CO + Cl2 = COCl2 equilibrium concentrations of reactants: [CO] = 0.20 mol/l; [Cl2] = 0.3 mol/L; [COCl2] = 1.2 mol/L. Calculate the system equilibrium constant and the initial concentrations of [CO] and [Cl2].
Task ID: 001604
Why does the N2 + 3H2 = 2NH3 equilibrium shift as the pressure changes and the N2 + O2 = 2NO equilibrium does not shift? Explain the answer based on the calculation of the forward and reverse reactions in these systems before and after the pressure changes. Write an expression for the equilibrium constants of each of these systems.
Task ID: 001606
During transportation of goods, from north to south the temperature increased by 20*C. Calculate the change in rate of possible reactions? The temperature coefficient of reaction rate is 4.
Task ID: 001608
How many times will the rate of chemical reaction A + 2B = C increase with increasing the pressure in the system 4 times and simultaneously increasing the temperature by 40*C? Reagents are gases. The reaction temperature is 2.
Task ID: 001610
In a homogeneous system CO (gas) + Cl2 (gas) = COCl2 (gas) equilibrium was established at [CO] = 0.20 mol/l; [Cl2] = 0.30 mol/L; [COCl2] = 1.2 mol/L. Calculate the isobaric potential of this reaction, provided that the equilibrium is established under standard conditions.
Task ID: 001611
The decomposition rate constant of N2O proceeding according to the equation 2N2O = 2N2 + O2 is 5*10^-4. Initial concentration [N2O] = 0.60 mol/l. Calculate the initial reaction rate and its rate when 50% N2O decomposes.
Task ID: 001612
For which reactions the equilibrium will shift towards the formation of the reaction products by compression of the gas mixture: a). Ca (NO3) 2 = CaO + 4NO2 + O2; b). C + O2 = CO2; c). N2O4 = 2NO2; d). CaCO3 = CaO + CO2? Justify the answer.
Task ID: 001617
In the synthesis of ammonia, under some conditions, 0.1 mol/l N2 are in equilibrium; 0.2 mol/l H2; 0.8 mol/l NH3. Calculate the equilibrium constant and calculate the initial concentrations of nitrogen and hydrogen.
Task ID: 001620
Calculate the change in the rate of chemical reaction 2CO (gas) + O2 (gas) = 2CO2 (gas) by reducing the pressure in the system (due to its expansion) by 10 times. The system temperature is kept constant.
Task ID: 001627
With the complete combustion of a certain amount of diborane B2H6 released 510 kJ of heat. The resulting boron oxide was fused with 42 g of baking soda. Calculate the mass of salt formed. (Q298(B2H6) = 2040 kJ/mol).
Task ID: 001632
Calculate the mass fraction (%) of the ferrule in the steel, which contains only ferrum and carbon, if 0.28 liters (0*C, 101325 Pa) of carbon dioxide is generated by burning 10 g of steel in the oxygen stream.
Task ID: 001633
Upon fusion of chromium (III) oxide weighing 3.05 g with an oxidizing agent in the presence of caustic soda sodium chromate weighing 6.37 g was obtained. Calculate the yield of the product in percent.
Task ID: 001636
Prove that the given metal (Zn) is located in the electrochemical series of stresses of metals to the dome. To make the redox reaction and the ionic equation of the reaction. Conclude.
Task ID: 001638
From 0.1250 g of the substance contains SiO2, Na2CO3, K2CO3 after treatment with hydrochloric acid and separation of the filtrate from SiO2 was obtained 0.1282 g of a mixture of KCl and NaCl. In this mixture, Cl-titration of 0.1003 n was calculated. 19.7 ml AgNO3 solution. Calculate the mass fraction (%) of SiO2, Na2CO3, K2CO3 in the original mixture.
Task ID: 001642
The organic matter contained in 3.77 g of mercury ointment was destroyed by HNO3. After dilution, Hg2+ was titrated, consuming 21.3 ml of 0.114 N. NH4SCN solution. Calculate the percentage of Hg and HgNO3 in the mercury sample.
Task ID: 001646
Methane, in the amount of 2000 m3 was subjected to pyrolysis. The degree of conversion of methane is 70%, the mass of ethine in the products of pyrolysis is 600 kg. Calculate the selectivity of the process.
Task ID: 001651
Consider the work of a galvanic element: Pb | Pb (NO3) 2 || Cd (NO3) 2 | Cd, electrolyte concentration [Pb2 +] = 0.01 M [Cd2+] = 0.5 M. Calculate the electrode potential of the galvanic element. Calculate the anode and cathode, record the processes occurring on the electrodes. Make a conditional graphical diagram of the galvanic element, indicate in it the charges of the electrodes and the direction of motion of electrons and ions. Calculate EMF.
Task ID: 001653
500 g of FeCl3 salt was diluted with water to 1 liter. Calculate the molar concentration of FeCl3, calculate how many 10×10 cm electronic boards can theoretically be poisoned in this solution. The etching area of copper is 90% of the area of the electronic circuit board, the thickness of the copper is 40 μm, the density of copper is 8.9 g/cm3.
Task ID: 001654
Calculate the number of moles of copper contained in 100 boards measuring 4×5 cm2. What volume of 2M FeCl3 solution is required to etch these boards. The etching area is 90%, the thickness of the copper layer is 50 μm, the density of copper is 8.9 g/cm3.
Task ID: 001658
A metal conductor made of cadmium was immersed in a 0.01 M solution of CdSO4 salt. Calculate the electrode potential of the electrode. Using a table of standard electrode potentials, draw up a diagram of a galvanic element in which this electrode is an anode. For the selected galvanic element, write down the equation of electrode processes and the general equation of the electrochemical process. Calculate the EMF value by taking the cathode electrode potential equal to the standard one. Calculate standard EMF?
Task ID: 001659
The electrolyte solution was electrolyzed at a current of 2A for 1 hour. Record the equation of electrode processes and the equation of solution electrolysis. Calculate the mass and volume of gas released at the anode. Fe(NO3) electrolyte 2.
Task ID: 001662
Write down the equation of the equilibrium constant for the reaction: C (s) + H2O (gas) = CO (gas) + H2 (gas). Calculate the equilibrium mixing under the conditions a). With increasing H2O; b). With decreasing temperature; if for the direct reaction ΔH <0.
Task ID: 001664
A solution of an unknown substance that does not conduct electrical current contains 0.2835 g of the substance in 2.565 g of water. The crystallization start temperature of this solution is Tkr = 272,777 K. Calculate the molar mass of the solute. Cryoscopic water constant 1.86.
Task ID: 001665
In what ratio are the boiling points of 0.01 molar aqueous solutions of glycerol (C3H8O3), nitric acid (HNO3) and formic acid (HCOOH)? Explain the answer. Ebuloscopic water constant 0.52.
Task ID: 001670
For saponification of 5.6 g of a mixture of ethyl esters of acetic acid and formic acid required 25.6 ml of a solution of NaOH with a mass fraction of 10% (ρ = 1.08 g/ml). Find the mass fraction of esters in the mixture.
Task ID: 001672
Calculate the mass fraction of H2O2 in pharmacy peroxide hydrogen solution if 25 ml of pharmacy solution was taken for preparation of 500 ml of solution and 9.40 ml of KMnO4 solution with molar concentration equivalent to 0.1 mol/l was taken to titrate 10 ml of the prepared solution, KMnO4 correction factor = 1.0203.
Task ID: 001673
Why is the electrical conductivity of a 20% solution of NaOH located between electrodes 2 cm2 apart at a distance of 8 cm equals if the electrical conductivity of this solution is 55.7 Ohm-1*cm2*g-eq-1. The density of the solution at an experiment temperature of 1.210 g/cm3.
Task ID: 001674
100 g of NaCl was dissolved in 10,000 l of water at 25*C. Consider this solution infinitely dilute. AND). Calculate the equivalent electrical conductivity of this solution. B). Calculate the specific electrical conductivity of the solution. IN). This solution is poured into a glass tube with an inside diameter of 4 cm, the ends of the tube are closed with electrodes, the distance between which is 20 cm. What is the current flowing through the solution if the potential difference between the electrodes is 80V? Use the Table of Limit Equivalent Electrical Conductivity of Ions (Ohm-1*cm2*g-eq-1) at 25*C (table provided in Art. 2).
Task ID: 001675
The electrical conductivity of 15% KNO3 solution at 18*C is 0.208 Ohm-1*cm-1. The density of the solution is 1,096 g/cm3. Calculate the value of equivalent electrical conductivity and the degree of dissociation of KNO3 in solution. Use the Table of Limit Equivalent Electrical Conductivity of Ions (Ohm-1*cm2*g-eq-1) at 25*C.
Task ID: 001676
The dissociation constant of the C3H7COOH butyric acid is 1.54*10^-5. Calculate the degree of dissociation of the aqueous solution at a dilution of 1024 l/g-eq, the concentration of hydrogen ions and the equivalent electrical conductivity at infinite dilution, if the specific conductivity of this solution is 4.2*10^-5 Ohm-1*cm-1.
Task ID: 001677
Using reference data on the equivalent electrical conductivity of ions in infinitely diluted solutions (table Limiting equivalent electrical conductivity of ions (Ohm-1*cm2*g-eq-1) at 25*C), what will be the course of the conductivity curve titration when interacting with the following aqueous solutions: AgNO3 + HCl; 2. BaCl2 + H2SO4.
Task ID: 001681
Task ID: 001681
Task ID: 001682
Graph the potentiometric titration curve of acetic acid solution with alkali solution. What will be the numerical value of pH at the equivalence point in this case? (Detailed solution with explanation and calculation of the potential of the glass electrode in the titration process and curve construction in accordance with the calculations, the calculation of the potential indicative – titration of 1 l 0.1 acetic acid solution 1 l 0.1 sodium hydroxide solution, this example can be calculated values potential of the glass electrode based on other data volumes and concentrations of solutions).
Task ID: 001684
To prepare the standard sodium carbonate solution, a sample of 1.3250 g of Na2CO3 was taken, dissolved and diluted with water in a 250 ml volumetric flask. Calculate the titer of sodium carbonate on hydrochloric acid.
Task ID: 001688
Calculate the mass fraction of O3 in the mixture of O3 and O2 if 11.2 liters of bp is required to burn a substance. mixtures of O3 and O2 or 61.6 liters at 0*C, 101325 Pa air (20% by volume of oxygen in the air).
Task ID: 001692
To a saturated solution of CaCl2 at a certain temperature was added CaCl2 and heated to complete dissolution and received 240 g of 37.5% solution. When the temperature of the solution decreased to the initial temperature, 116.8 g of a precipitate of CaCl2*6H2O dropped. Calculate the mass of CaCl2 added to the stock solution.
Task ID: 001693
Calculate the mass of cumene if obtained from acetylene benzene (yield 80%), benzene cumene (yield 75%) from cumene phenol (yield 66.7%). The mass of phenol is 60.6 g less than the mass of the original compound.
Task ID: 001694
Obtaining sulfuric acid from pyrite occurs in 3 stages. With product yields 66.7%, 75% and 80% respectively. Find the mass of oleum with H2SO4*0.2SO3 if it is less than the mass of the starting material by 44 g.
Task ID: 001697
A portion of CaCO3 marble is dissolved in a solution of HCl with a molar concentration of 0.04 mol/l. With complete dissolution of the sample, 0.3 l of carbon dioxide, measured at a temperature of 27*C and a pressure of 83.1 kPa, was released. Write the reaction equation. Calculate how many moles of carbon dioxide are released, how many liters of acid are taken for the reaction, which is the final molar concentration of the salt.
Task ID: 001700
Calculate the active and titratable alkalinity of urine with a pH of 7.8 if 1.5 ml of a solution of hydrochloric acid with a molar concentration of 0.1 mol/l is consumed for a 5 ml titration.
Task ID: 001702
Based on the values of the standard enthalpy and entropy of the formation of substances to calculate the possibility of reaction of reduction of TiO2 with carbon at a temperature of 1500K.
Task ID: 001703
Chemical metallization with silver, sputtering method. Part of technology: Chemical composition and technology of preparation of solutions for chemical metallization with silver: Activator; Recovery; Oxidant. SMPL TECHNOLOGICAL UNIT No. 02-0003-27.03.2010 chemical composition and solution preparation technology for SMPL (Silver Mirror for Polymer Layer) Developer: techemy Date: 27.03.2010 (Russian)
Task ID: 001707
Chromium reacts with iodine according to the equation 2Cr + 3I2 = 2CrI3. What is the volume of gaseous iodine at 0*C, 101325 Pa will need to react with 11 g of metallic chromium without impurities.
Task ID: 001708
What products are formed by electrolysis of sodium sulfate solution. The electrodes are inert. Write down the flow charts of the processes running on the anode and cathode and the flow chart.
Task ID: 001712
Calculate the change in Gibbs energy and calculate the feasibility of the process of obtaining magnesium titanium in a thermal way – the restoration of titanium (IV) chloride with metallic magnesium at 1000K.
Task ID: 001714
A metal conductor made of nickel immersed in a 0.001 M solution of NiCl2 salt. Calculate the electrode potential of a given electrode. Using a table of standard electrode potentials, draw up a diagram of a galvanic element in which the electrode is an anode. For the selected galvanic element, write down the equation of the electrode processes and the equation of the electrochemical process. Calculate the EMF value by taking the electrode potential of the cathode equal to the standard one. Why is the standard EMF?
Task ID: 001716
Calculate the cost of technical Na2SO4 with a mass fraction of 95% and electrolytic hydrogen (H2 content – 97% (wt.)) Per 1 ton of technical Na2S 96%, which is formed during the reaction: Na2SO4 + 4H2 = Na2S + 4H2O2 % Na2SO4 and H2 from the theoretically necessary amount to obtain 1 ton of technical Na2S.
Task ID: 001717
Prolonged heating of a sample of some phenol X weighing 1.1 g with an excess of ammonia solution of Ag2O produces 2.16 g of silver. Boiling the same phenol with aqua regia results in the formation of a yellow, insoluble compound Y containing Cl 57.7% and C 29.3% (by mass). Adding 1.23 g of substance Y to an excess of KI solution causes a brown color, which disappears when 4 ml of 1.25 mol/L K2SO3 solution is added. Heating of substance Y with cyclohexa-1,4-diene leads to the formation of two compounds A and B, which are resistant to bromine water. Set the structural formulas of compounds X and Y, A and B. Write the equation for the reactions.
Task ID: 001719
Inks for PVC inscriptions. Inks are used by employees of power supply companies, auto-electricians, electricians-installers, workshop electricians to mark electrical wires. Ink is made using ink pen. After the ink has dried (10-40 C. Depending on the air temperature), the inscription made is practically impossible to remove from the PVC surface either mechanically or by solvents. Inks are resistant to sunlight, moisture, the effects of org vapor. solvents (gasoline, etc.). Even if the inscription on the PVC was accidentally painted with paint, having removed the paint mechanically, the ink inscription would remain intact (Russian).
Task ID: 001724
For titration of 200.0 ml of industrial water in the presence of methyl orange spent 10.00 ml of HCl with a titer of 1.760 mg/ml. Calculate the temporary rigidity of the analyzed water.
Task ID: 001726
How many ml of 0.11M NaOH solution will titrate excess HCl after the interaction of 0.3 g of a mixture having a composition of 35.5% Na2CO3 and 42.0% NaOH, with 25 ml of 0.2400 N. HCl solution?
Task ID: 001727
Make a material balance for the process of extraction of Zn2+ from a solution of 1000 m3, p = 1.10 g/cm3 containing 7% ZnCl2 and 10% NaCl. Precipitated with NaOH solution with Cm = 1 mol/l. p = 1.05 g/cm3.
Task ID: 001728
Calculate the mass of H2O2 in a 120 ml solution if 8.12 ml of KMnO4 titrant (W) = 0.034 mol/L is consumed for titration of a 10.0 ml solution. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) expression of the law of equivalents for reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001729
How will the rate of reaction of SO2 + 2H2S = 3S + 2H2O change if: a) increase the concentration of sulfur (IV) oxide 3 times; b) increase the concentration of hydrogen sulfur 3 times; c) increase the concentration of sulfur (IV) oxide and hydrogen sulfur 3 times?
Task ID: 001730
1 liter the aqueous solution contains 577 g of H2SO4. The density of the solution is 1,335 g/cm3. Calculate the mass, mole fraction (%) of the substance in solution, molar concentration, equivalent concentration and molality of solution.
Task ID: 001732
The galvanic element consists of zinc immersed in 0.1M Zn(NO3)2 and a hydrogen electrode with pH = 1. Draw a diagram, write the electrode process equation and calculate the EMF of the element. (φ0(Zn2+/Zn) = – 0.76 B)
Task ID: 001733
How is the corrosion of zinc in contact with cadmium in neutral and acidic media (HCl solution)? What metal is a cathode, which anode? To compose electronic equations of anode and cathode processes. What is the composition of corrosion products? φ0(Zn2+/Zn) = – 0,76 B, φ0(Cd2+/Cd) = -0,40 B.
Task ID: 001734
What is the mass of copper released on the cathode by CuSO4 electrolysis for 1 hour. At a current of 4 A? To make electronic equations of the processes occurring on the electrodes (inert electrodes).
Task ID: 001736
Calculate the entropy change when heating 1.2 mol SO2 from temperature T1 = 175K to T2 = 285K, at P = 1.013*10^5 Pa, molar heat of melting ΔHmt. = 7.434 J/mol and the molar heat of evaporation is ΔHgas. = 25.05 J/mol. The dependence of the heat capacity on the temperature for the gaseous state Cp = a + W + s*/ T^2 taken from the reference book: Wed(s) = 11,47 J/mol*K, Wed(liquid) = 13,99 J/mol*K.
Task ID: 001737
Using thermodynamic reference tables, calculate the process direction under standard conditions at temperature T = 1230K for the chemical reaction 2FeO (s) + H2O (gas) = Fe2O3 (s) + H2 (gas) Calculate the chemical equilibrium constant.
Task ID: 001738
What is the amount of heat released by cooling 1250 grams of water vapor from 307*C to 20*C at a constant pressure of 1,013*10^5 Pa. If the specific heat of evaporation of water Q(H2O)gas = 2260 J/h. The dependence of the true heat on the temperature for the vapor and the liquid state is expressed by the equations of the form Cp = a + W + C ‘/ T^2 taken from the reference.
Task ID: 001740
Calculate the mass of the sample, which contains about 65% MnO2, that after interaction with 50,00 ml of 0.1 M H2C2O4 (feq = 1/2), the excess of it should be titrated with 25.00 ml of KMnO4 solution (1.00 ml of KMnO4 solution is equivalent to 1, 05 ml of H2C2O4 solution).
Task ID: 001741
Anhydrous chloride of some metal contains 74.7% chlorine. Calculate the mass fraction and the molar concentration of the solution formed by dissolving 30 g of hexahydrate of this chloride in 70 g H2O (solution density 1.04 g/ml).
Task ID: 001742
Combustion of 4 organic compounds results in a mixture of gases having the same hydrogen density and containing only CO2 and H2O in a 2 : 3 molar ratio. Suggest formulas if the first two are gases. To make the equation of reactions of interaction of substances in a liquid state with sodium.
Task ID: 001744
Calculate the mean value of the reaction rate constant of the catalytic decomposition of hydrogen peroxide in aqueous solution and the reaction order if the following volumes of potassium permanganate solution of molar concentration of 0.0015 mol/dm3 were consistently consumed for the titration of samples of hydrogen peroxide in a volume of 2 ml (table with data in the condition of the problem).
Task ID: 001745
At the plant for the production of ammonia, with a capacity of 250 tons/day. nitrogen, the residual oxygen content of which is 0.8%. Practical cost of nitrogen-hydrogen mixture is 3000 m3 (0*C, 101325 Pa) for the production of 1 ton of H3. Calculate the daily air requirement (nitrogen and oxygen volumes of 80% and 20%, respectively) required for nitrogen production.
Task ID: 001746
A gas mixture containing 7% SO2, 11% O2 and 82% N2 enters the contact apparatus where 97% SO2 is oxidized to SO3. Calculate the composition of the gas mixture at the outlet of the contact apparatus.
Task ID: 001747
Calculate Cr, Xc of the dissociation reaction 2HBr (gas) = H2 (gas) + Br2 (gas) if the initial concentration of substance C0 (HBr) = 0.68 mol/l, the degree of dissociation HBr a = 2.54*10^-2. Calculate the direction of reaction under standard conditions at T = 500K and P = 1,013*10^5 Pa.
Task ID: 001748
For the chemical reaction 2SO2 (gas) + O2 (gas) = 2SO3 (gas) the dependence of the equilibrium constant on the temperature is expressed by the equation lgKp = 10373/T + 1,22lgT-13,8. Obtain the equation of temperature dependence for the thermal effect of the reaction, the change in the Gibbs free energy, the entropy, and the heat capacity of the process. Calculate the value of the equilibrium constant and thermodynamic functions at 700K.
Task ID: 001749
The equilibrium constant of the chemical reaction N2 (gas) + 3H2 (gas) = 2NH3 (gas) at T = 673K equals Kr = 0.8*10^-5. To calculate Xc, will the formation of reaction products under the perfectly reversible process if the initial partial pressures of substances in Pa level PNH3 = 0.9*10^5; PN2 = 0.34*10^5; PH2 = 0.72*10^5?
Task ID: 001750
Calculate the change in the standard enthalpy and the change in the standard entropy of the reaction: 6CO2 (gas) + 6H2O (liquid) = C6H12O6 (s) + 6O2 (gas). Is it possible to have a spontaneous process? Calculate which of the thermodynamic factors (enthalpy or entropy) is decisive in the process. Write the thermochemical equation of the process.
Task ID: 001751
For the decomposition reaction of acetone decicarboxylic acid CO(CH2CO2H) 3 = CO(CH3) 2 + 2CO2 k1 = 2.46e-5 min-1 (at T1 = 273.5K) and k2 = 5.76e-3 min-1 ( at T2 = 313.2K). Calculate the time during which the reaction will occur by 70% at T3 = 325K.
Task ID: 001753
Calculate the molar concentration of potassium sulfite equivalent if titration of an aliquot part of a solution of this substance with a volume of 10.0 ml consumes 10.17 ml of a titrant of potassium permanganate (c1/Zt) = 0.0950 mol/l. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001754
Calculate the standard enthalpy of benzene hydrogenation using the two consequences of Hess’s law. Specify the type of reaction (exo or endothermic). Write the thermochemical equation of the process.
Task ID: 001755
The activation energy of sucrose hydrolysis in acidic solution is 107 kJ/mol. The presence of the fructofuranose enzyme reduces the activation energy to 40 kJ/mol. How many times will the half-life at 310 K be reduced for the catalytic reaction? Consider that the pre-exponential factor does not change.
Task ID: 001757
Calculate the mass fraction in an aqueous solution of lithium nitrite, 200 ml volume (solution density 1,119 g/ml), if titration of 15 ml aliquots of a solution of this substance consumes 16,21 ml of titrant potassium permanganate (c1/zT) = 0,099 mol/l. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001759
The first order reaction takes place at 20% for 25 minutes at 45*C and 35% for 5 minutes at 75*C. Calculate the activation energy and temperature coefficient in the specified temperature range.
Task ID: 001760
An aqueous solution of potassium sulfate with a mass fraction of 3.5% has an osmotic pressure of 1154 kPa at room temperature. Calculate the isotonic coefficient of potassium sulfate in solution at a density of 1.154 g/ml.
Task ID: 001761
Calculate the mass of sodium hydroxide in a solution of 150 ml if 10.36 ml of sulfuric acid titrant (c1/zT) = 0.103 mol/l is used to titrate an aliquot part of a solution of this substance with a volume of 15.0 ml. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001762
Calculate the temperature at which both directions of the ethyl acetate hydrolysis reaction are equally likely. Which of the thermodynamic factors (enthalpy or entropy) is decisive? Specify the type of process (exo- or endothermic).
Task ID: 001763
First order reaction. In 3 hours the concentration of reagents decreased by 30% at 298K. Find the activation energy of this reaction if 45 minutes are required to achieve this result. at a temperature of 310K.
Task ID: 001765
Calculate the mass fraction of ammonia in a sample weighing 5.5 g if this sample is diluted with water in a 200 ml volumetric flask. Titration of an aliquot part of a solution of this substance with a volume of 10.0 ml consumed 12.17 ml of titrant of sulfuric acid (c1/zT) = 0.075 mol/l. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001769
Calculate the molar concentration of sodium carbonate equivalent if titration of an aliquot part of a solution of this substance with a volume of 10.0 ml consumes 10.17 ml of titrant of sulfuric acid (c1/z T) = 0.095 mol/l. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001770
Which of the thermodynamic factors (enthalpy or entropy) is decisive in the process of propane recovery. Write the thermochemical equation of the process. Specify the type of process (exo- or endothermic).
Task ID: 001771
The concentration of amyl acetate during acid hydrolysis was varied as follows (table data in the condition of the problem). Calculate: a) the order of the kinetic equation; b) semi-transformation period; C) acid concentration after 1.5 hours. Write the kinetic equation.
Task ID: 001772
Find the activity of Ca2+, Cl- ions in a calcium chloride solution of 500 ml at a concentration of 0.001 mol/l, to which the same volume of solution containing 0.82 g of sodium acetate is added.
Task ID: 001773
Calculate the mass fraction of NH4Cl in a 12.5 g sample if this sample is diluted with water in a 100 ml volumetric flask. Titration of an aliquot portion of a solution of this substance with a volume of 5.0 ml consumed 7.34 ml of NaOH titrant (c1/zT) = 0.05 mol/l. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001774
Calculate the standard enthalpy of the acetone (liquid) reduction reaction in propan-2-ol (liquid) using the two consequences of Hess’s law. Specify the type of reaction (exo or endothermic). Write the thermochemical equation of the process.
Task ID: 001775
The rate constant of the reaction of thermal decomposition of ethyl chloride into ethylene and hydrogen chloride is 4.14*10^-5 s -1 at 700K. Calculate: a) the time for which 30% of the starting material will decompose; b) what part (%) will decompose after 10 min. after the start of the reaction; c) the activation energy of the reaction, if the pre-exponential factor is 1.3*10^10 s-1.
Task ID: 001777
Calculate the molar concentration of H2S equivalent if 10.17 ml of sodium hydroxide titrant (c1/zT) = 0.095 mol/L is used to titrate an aliquot part of a 10.0 ml solution of this substance. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001778
Calculate the temperature at which both directions of the methane chlorination reaction in the first degree are likely. Which of the thermodynamic factors (enthalpy or entropy) is decisive? Specify the type of process (exo- or endothermic).
Task ID: 001779
Using the information given on the reaction of the decomposition of ethane in the gas phase into ethylene and hydrogen under standard conditions (table data in the condition of the problem). Calculate: a) the order of the kinetic equation; b) the equilibrium constant of the process; c) calculate the rate constant at 1250 K if Ea = 83.2 kJ/mol.
Task ID: 001780
Derive the molecular formula of altrose having the composition Cn (H2O) n if it is known that the freezing point of the solution containing 24 g of altrose in 0.9 kg of water is 0.276K. Conclude the behavior of erythrocytes in this solution at 18*C.
Task ID: 001781
Calculate the mass of NH4I in 100 ml solution if 10.15 ml of barium hydroxide titrant (c1/zT) = 0.003 mol/L is consumed for titration of an aliquot of 10.0 ml solution of this substance. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001783
The rate constant of hydrolysis of atropine at 40*C is 0.316 s-1. How many times will the initial concentration of atropine decrease after 12.8 seconds? What will be the half-life of this reaction? Find the activation energy of the hydrolysis reaction if, at 60*C, the rate constant is 0.373 s-1.
Task ID: 001784
What mass of sorbitol should be contained in 5 l of aqueous solution so that it is isotonic to a solution of barium chloride with C (BaCl2) = 0.01 mol/l, the isotonic electrolyte ratio is 2.91.
Task ID: 001785
Calculate the mass fraction of formic acid in a sample weighing 2.5 g diluted with water in a volumetric flask up to 150 ml if 9.15 ml of potassium permanganate titrant (c1/zT) = 0.0025 mol/L. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001786
At room temperature, the equilibrium concentrations in the system: 2SO2 + O2 = 2SO3 (all gases) were C(CO2) = 0.01 mol/l; C(O2) = 0.06 mol/l; C(SO3) = 0.02 mol/l. What will be the direction of the process at concentrations equal to 0.06 mol/l for all substances? Will the reaction be ergonomic or exergonic?
Task ID: 001787
The half-life of the plumum from blood and soft tissues at 310K is 22 days. Assuming that the process is described by the first-order kinetic equation, calculate how much plumbum (% of baseline) will be output after 10 days at this temperature?
Task ID: 001788
The isotonic coefficient of potassium sulfite in aqueous solution containing 1,352 g of salt in 500 ml of water is equal to 2.87. Calculate the freezing point of this solution. The density of the solution is 1.1 g/ml. Find the osmolarity of this solution at 320K and a pressure of 840 kPa.
Task ID: 001789
Calculate the mass fraction of H2SO4 in 120 ml of solution if 17.10 ml of NaOH titrant (c1/zT) = 0.05 mol/L is consumed for a titration of 15 ml of this solution. The density of the solution H2SO4 = 1,174 g/ml. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac).
Task ID: 001790
Calculate in two ways (using standard enthalpy of formation and standard enthalpy of combustion) the standard enthalpy of the trimerization reaction is to obtain benzene (liquid) from acetylene (gas). Exo- or endothermic reaction?
Task ID: 001791
A ferrum that is trapped in the cells of a mononuclear phagocyte system either quickly returns to circulation (a half-life of 34 minutes) or is postponed to a stock (half-life of 7 days). The processes follow the first-order equation at 310K. Calculate the rate constants of both processes at a given temperature and bring their values to the same units. Calculate how much ferment (in% of baseline) will return to circulation in 5 days at this temperature?
Task ID: 001793
Give an example of a buffer system capable of maintaining pH in the 7-8 range. Calculate the pH of this buffer system if the ratio of concentration components is 3. Suggest a method for preparing such a buffer system.
Task ID: 001795
Give examples of redox systems operating under normal conditions in the body (at least 2). Is it possible under standard conditions for the body to oxidize malate to oxaloacetate with oxygen in an acidic environment? Justify the answer.
Task ID: 001797
Specify which of the following acids has the maximum value of the degree of dissociation: formic, hydrogen fluoride, hydrogen cyanide, acetic acid (at acid concentrations of 0.1 mol/l). Explain the answer. Calculate the pH of the solution of the selected acid.
Task ID: 001798
Give examples of two competing heterogeneous processes for a common cation. Specify the competing particles which process prevails. Explain the answer. Give the expression of the solubility constant for the compound formed.
Task ID: 001799
Give an example of a type II redox system. Calculate the value of the redox potential of the system containing the oxidized and reduced forms in the ratio of 2/3 and at pH = 7 (T = 310K).
Task ID: 001801
In what ratio of concentrations of sodium dihydrophosphate and sodium hydroxide is a buffer system formed 1 : 1, 10 : 1, 1 : 2? Write the reaction equation, calculate the pH of the solutions obtained.
Task ID: 001805
Compare the two types of resilience of dispersed systems. What actions can be taken to break stability? Coagulating ability of magnesium ions with respect to sol aurum (III) sulfide 1,42 l/mol. What volume of magnesium chloride solution with Cm = 0.02 mol/l is required to coagulate a sol of 1 liter?
Task ID: 001806
Two flasks contain 10 ml of acetic acid solution Cm = 0.1 mol/l. To each flask was added a solution of KOH cm = 0.05 mol/l of the following volumes: a) 15 ml; b) 20 ml. Which of the resulting solutions will be buffered? Confirm the answer with calculations.
Task ID: 001810
What is the minimum volume of 0.01 mol/l potassium dichromate solution to be taken to coagulate the 1 liter hydroxol ferum (III) hydroxide if the dichromate ion coagulation threshold is 0.06 mmol/l?
Task ID: 001812
Specify the conditions for the dissolution of the TlCl precipitate. What concentration of thallium ions do you need to reach to obtain a precipitate of thallium chloride from a solution of potassium chloride at a concentration of 0.006 mol/l?
Task ID: 001814
What is adsorbent and adsorption? Give examples (at least 2). To a solution of acetic acid with a volume of 50 ml with Cm = 0.1 mol/l was added activated carbon with a mass of 2 g.,05 mol/l. Calculate the amount of acid adsorption.
Task ID: 001815
Which dispersion systems include fog and smoke: a) the particle size of the dispersed phase; b) the aggregate state of the dispersed phase and the dispersed medium? Justify the answer. Calculate the degree of dispersion of the system with an average diameter of spherical particles 2.5e-4 m. What is the dispersion system?
Task ID: 001816
Give a system consisting of a weak acid and an excess of hydroxide capable of maintaining a pH in the range of 4-5. Calculate the pH of this buffer system if the concentration ratio of the components is 2.
Task ID: 001818
Adding which reagents to the solution containing Fe3+ and Ni2 + ions will produce a common ligand-exchange equilibrium? Explain. Write the reaction equation and the expression of the equilibrium constant for the selected case.
Task ID: 001820
What are surface phenomena? With increasing concentration of isobutyric acid solution from 0.125 mol/l to 0.250 mol/l, its surface tension decreased from 55.1 mN/m to 47.8 mN/m, and in isovaleric acid solution from 43.2 mN/m to 35,0 mN/m. Compare the adsorption values of the substances in the given concentration range at T = 293K.
Task ID: 001821
What electrokinetic phenomena are observed in sols? In electrophoresis, sol particles of bromide argentum obtained by mixing equal volumes of potassium bromide solutions with Cm = 0.002 mol/l and nitrate argentum are transferred to the anode. In what range is the concentration of nitrate argentum solution? Write a diagram of the structure of the micelle of this sol with explanation.
Task ID: 001822
Specify which of the following acids has the maximum value of the ionization constant: formic, oxalic, cyanide hydrogen, acetic acid? Explain. Calculate the pH of the solution of the selected acid.
Task ID: 001823
What is called the stability constant of the complex? How are stability and instability constants related? Name the complex compound (NH4)2[Pb(CH3COO)4]. Specify its complexing agent, ligands, outer and inner spheres. Write the dissociation equation.
Task ID: 001825
Give an example of a first-rate redox system. Calculate the value of the redox potential of this system at the temperature of the physiological norm, if the ratio of concentrations of oxidized and reduced forms is 3: 2.
Task ID: 001826
A solution of aluminum chloride was added to the precipitate of aluminum hydroxide to allow adsorption peptization. Write possible formulas for micelles. Compare the coagulating ability of the K2SO4 and CaCl2 electrolytes for the sols obtained.
Task ID: 001827
What factors calculate the coagulating ability of the electrolyte? Coagulation of sol aurum (III) sulfide with a volume of 50 ml occurred when adding a solution of chromium (III) sulfate volume of 1.0 ml with cm = 0.02 mol/l. Calculate the coagulating ability of the sulfate ions with respect to this sol.
Task ID: 001830
As a result of the melting of 24 g of sodium salt of saturated mono-carboxylic acid with sodium hydroxide taken in excess, 3858 ml (0*C, 101325 Pa) of gas was released, accounting for 79% of the theoretical yield. Calculate the mass of gas generated
Task ID: 001831
Calculate the expected ratio of products of the reaction of monochlorination of isopentane in percent, if it is known that the relative reactivity of tertiary, secondary and primary hydrogen atoms to substitution with chlorine is 5 : 4 : 1.
Task ID: 001832
The mass fraction of carbon in hydrocarbons is 83.33%. The vapor density of the substance in hydrogen is 36. Calculate the formula of the hydrocarbon, write the structural formulas of all its isomers and name them according to the IUPAC nomenclature.
Task ID: 001833
Combustion of a substance containing carbon, hydrogen, and chlorine resulted in 0.44 g of carbon (IV) oxide and 0.18 g of water. From the chlorine contained in this mass of the substance, after its conversion into a chloride ion, 2.86 g of chloride is obtained. Calculate the formula of the substance.
Task ID: 001834
The gas mixture consists of propane and butane. Combustion of 100.8 cm3 of this mixture yielded 336 cm3 of carbon (IV) oxide. Calculate the composition of the mixture (as a percentage by volume).
Task ID: 001836
Under laboratory conditions, the basic salt of CuCO3*Cu(OH)2 is obtained by the interaction of cuprum (II) sulfate and soda: 2CuSO4 + 2Na2CO3 + H2O = CuCO3*Cu(OH)2 + 2Na2SO4 + CO2. Calculate the mass of soda that has reacted to form 10 g of basic salt.
Task ID: 001841
Calculate the heat of formation of carbon dioxide CO2 (g), based on thermochemical equations: H2 (g) + 0,5O2 (g) = H2O (g), ∆H = -285,84 kJ; CH4 (g) + 2O2 (g) = 2H2O (liq) + CO2 (g), ∆H = -890.31 kJ; C (s) + 2H2 (g) = CH4 (g), ∆H = -74.68 kJ.
Task ID: 001842
Calculate the thermal effect of the reaction by the known values of the standard heat of formation of the starting materials and reaction products: 2H2O2 (liq) = O2 (g) + 2H2O (liq).
Task ID: 001846
At some temperature, the equilibrium constant of the system N2 + O2 = 2NO equals 0200. Calculate the equilibrium concentrations of all components of the system if the initial concentrations of nitrogen and oxygen are the same and are 1 mol/l.
Task ID: 001848
With the dissolution of 15 g of chloroform in 400 g of diethyl ether (ether), the boiling point increased by 0.665*C. Calculate the molar mass of chloroform. Ebuloscopic ether became 2.12*C*kg/mol.
Task ID: 001856
Golden plating spray. Part of the technology being developed is the reaction of a chemical gold mirror. Many options for reducing agents have been tested under various conditions. The file present the result that gave the best quality coating gold mirror. The reaction is not finalized. The mechanism of the chemical reaction is unknown and other characteristics of the reaction have not been clarified. Despite this, we have a result. Perhaps you can refine the reaction and improve its characteristics based on the information in the file.
Task ID: 001882
Calculate the enthalpy of combustion of methane, ethane, propane, butane and their mixture, which corresponds to the composition of natural gas: methane (96.5%), ethane (1.56%), propane (0.44%), butane (0.15%) ). How much heat will be released during the combustion of 1 m3 of each of the gases and 1 m3 (one cubic meter) of natural gas?