Chapter 17 Homework Problems

1) Write equilibrium constant expressions for the following gas phase reactions:(a) 2H2(g) + O2(g) 2H2O(g)(b) Xe(g) + 3F2(g) XeF6(g)(c) 2C6 H6(g) + 15O2(g) 12CO2(g) + 6H2O(g)

2) Write equilibrium constant expressions for the following reactions:(a) Zn(s) + 2Ag+(aq) Zn+2(aq) + 2Ag(s)(b) VO34 (aq) + H2O(l) VO3(OH)2(aq) + OH(aq)(c) 2As(OH)36 (aq) + 6CO2(g) As2O3(s) + 6HCO3(aq) + 3H2O(l)

3) At 45 4 K , Al2Cl6(g) reacts to form Al3Cl9(g) according to the equation3Al2Cl6(g) 2Al3Cl9(g)In an experiment at this temperature, the equilibrium partial pressure of Al2Cl6(g) is 1. 00 atm, and the equilibrium partial pres-sure of Al3Cl9(g) is 1. 02 102 atm. Compute the value of the equilibrium constant for the above reaction at 45 4 K .

4) The compound 1, 3-di-t-butylcyclohexane exists in two forms that are known as the "chair" and "boat" conformations becausethe molecular structures resemble these objects. Equilibrium exists between these forms, represented by the equationchair boatAt 580 K , 6. 42% of the molecules are in the chair form. Calculate the value of the equilibrium constant for the reaction as writ-ten above.

5) A certain amount of NOBr(g) is sealed in a flask, and the temperature is raised to 35 0 K . The following equilibrium is estab-lished:NOBr(g) NO(g) + 12 Br2(g)The total pressure in the flask when equilibrium is reached at this temperature is 0. 675 atm, and the vapor density is 2. 219 g/L.(a) Calculate the partial pressure of each species.

(Hint: the vapor density cant change in a gas phase reaction is the volume is fixed.)(b) Calculate the value of the equilibrium constant at this temperature.

6) At 133 0 K , germanium(II) oxide (GeO) and tungsten(VI) oxide (W2O6) are both gases. The following two equilibria are estab-lished simultaneously:2GeO(g) + W2O6(g) 2GeWO4(g)GeO(g) + W2O6(g) GeW2O7(g)The equilibrium constants for the two are 7. 0 103 and 38 103, respectively. Compute K for the reaction:GeO(g) + GeW2O7(g) 2GeWO4(g)

7) The compound phosgene (COCl2(g)) is an important intermediate in the manufacture of certain plastics. It is produced by thereactionCO(g) + Cl2(g) COCl2(g)for which the equilibrium constant has the value K = 0. 20 at 600C.(a) Calculate the partial pressure of phosgene that is in equilibrium with a mixture of 0. 025 atm of carbon monoxide and0. 003 5 atm of chlorine at 600C.(b) Calculate the total pressure in this reaction system, assuming that no gases other than the three mentioned above are present.

8) The reactionSO2Cl2(g) SO2(g) + Cl2(g)has an equilibrium constant at 100C of 2. 40.(a) Suppose that an initial partial pressure of SO2Cl2 in a reaction tank with rigid walls is 1. 500 atm and that no other species arepresent. Calculate the reaction quotient, Q, and state whether the total pressure increases or decreases as the reaction tendstoward equilibrium.(b) Calculate the partial pressures of SO2Cl2, SO2, and Cl2 when equilibrium is reached.

9) The dehydrogenation of benzyl alcohol to make the flavoring agent benzaldehyde is an equilibrium process described by theequationC6 H5CH2OH(g) C6 H5CHO(g) + H2(g)At 523 K , the value of its equilibrium constant is K = 0. 558.(a) Suppose 1. 20 g of benzyl alcohol is placed in a 2. 00 L vessel and heated to 523 K . What is the partial pressure of benzalde-hyde when equilibrium is attained?(b) What fraction of benzyl alcohol is dissociated into products at equilibrium?

10) Suppose 93. 0 g of HI (g) is placed in a glass vessel and heated to 11 07 K . At this temperature, equilibrium is quickly establishedbetween HI (g) and its decomposition products, H2(g) and I2(g):2HI (g) H2(g) + I2(g)

General Chemistry II & Lab Spring 2014CHEM-UA 126 Prof. Halpin

The equilibrium constant at 11 07 K is 0. 025 9, and the total pressure at equilibrium is observed to equal 6. 45 atm.(a) Calculate the equilibrium partial pressures of HI (g), H2(g), and I2(g).(b) Calculate the volume of the vessel.

11) The equilibrium constant at 35 0 K for the reactionBr2(g) + I2(g) 2IBr(g)has a value of 322. Bromine at an initial pressure of 0. 0500 atm is mixed with iodine at an initial partial pressure of 0. 0400 atmand held at 35 0 K until equilibrium is reached. Calculate the equilibrium pressure of each of the gases.

12) The following reaction is exothermic:3NO(g) N2O(g) + NO2(g)Predict and explain the effect of each of the following stresses on the position of equilibrium.(a) N2O(g) is added to the equilibrium mixture without change of volume or temperature.(b) The volume of the equilibrium mixture is reduced at constant temperature.(c) The temperature of the equilibrium mixture is decreased.(d) Gaseous argon (which does not react) is added to the equilibrium mixture while keeping both the total gas pressure and thetemperature constant.(e) Gaseous argon is added to the equilibrium mixture without changing the volume.

13) The following reaction is endothermic:SO3(g) SO2(g) + 12 O2(g)Predict and explain the effect of each of the following stresses on the position of equilibrium.(a) O2(g) is added to the equilibrium mixture without change of volume or temperature.(b) The mixture is compressed at constant temperature.(c) The equilibrium mixture is cooled.(d) An inert gas is pumped into the equilibrium mixture while keeping the total gas pressure and the temperature constant.(e) An inert gas is added to the equilibrium mixture without changing the volume.

14) The equilibrium constant for the "water gas" reactionC(s) + H2O(g) CO(g) + H2(g)is K = 2. 6 at a temperature of 1000 K . Calculate the reaction quotient Q for each of the following conditions, and state whichdirection the reaction shifts in coming to equilibrium:(a) PH2O = 0. 600 atm, PCO = 1. 525 atm, PH2 = 0. 805 atm.(b) PH2O = 0. 724 atm, PCO = 1. 714 atm, PH2 = 1. 383 atm.

15) Pure solid NH4 HSe is placed in an evacuated container at 24.8C. Eventually, the pressure above the solid reaches 0. 018 4 atm,thanks to the reactionNH4 HSe(s) NH3(g) + H2Se(g)This pressure is the equilibrium pressure in the container.(a) Calculate the value of the equilibrium constant of this reaction at 24.8C.(b) In a different container, the partial pressure of NH3(g) in equilibrium with NH4 HSe(s) at 24. 8C is 0. 025 2 atm. What is thepartial pressure of H2Se(g)?

16) The total pressure of gases in equilibrium with solid sodium hydrogen carbonate at 11 0. 0C is 1. 648 atm, corresponding to thereaction2NaHCO3(s) Na2CO3(s) + H2O(g) + CO2(g)(NaHCO3 is used in dry chemical fire extinguishers because the products of this decomposition reaction smother the fire.)(a) Calculate the value of the equilibrium constant at 11 0. 0C.(b) What is the partial pressure of water vapor in equilibrium with NaHCO3(s) at 110. 0C if the partial pressure of CO2(g) is0. 800 atm?

17) At 100C, K = 1. 5 108 for the reactionCO(g) + Cl2(g) COCl2(g).

Calculate the partial pressure of CO(g) if a vessel containing only COCl2(g) at 0. 250 atm is heated to 100C and the reactionproceeds to equilibrium.

18) At high temperature, HCl and O2 react as4HCl(g) + O2(g) 2Cl2(g) + 2H2O(g)

If HCl at 2. 30 atm and O2(g) at 1. 00 atm react at 75 0 K , the equilibrium pressure of Cl2(g) is 0. 93 atm. Calculate K .19) At elevated temperature, carbon tetrachloride decomposes to its elements:

CCl4(g) C(s) + 2Cl2(g).At 700 K , if the initial pressure of CCl4 is 1. 00 atm and at equilibrium the total pressure is 1. 35 atm, then calculate K .

20) At 395 K , K = 1. 83 103 for the reactionPCl5(g) PCl3(g) + Cl2(g).

If 2. 00 g of PCl5 is placed in a 3. 00 L bulb at 395 K , calculate the equilibrium partial pressure of Cl2.