AP ChemistryName :

Worksheet : Ch 13 : obj. 4-10Date :

_____ 1. If, at a given temperature, the equilibrium constant for the reactionH2 (g) + Cl2 (g)  2HCl(g)is Kp, then the equilibrium constant for the reaction HCl(g)  (1/2)H2 (g) + (1/2)Cl2(g) can be represented as:

a. __1__ b. KP2 c. ___1__ d.

_____ 2. For the reaction H2O(g) + Cl2O(g)↔ 2HOCl(g), K = 1.20 at 300.K. What is the value of Kp 300.K?

a. 1040b. 1.20c. 7.47 x 106d. 0.00120

3. For the reaction below, KP = 1.16 atm at 800 ºC.

CaCO3(s) ↔CaO(s) + CO2(g)

If a 60.0 gram sample of CaCO3 is put into a 40.0 liter container and heated to 850. ºC, what percent of the CaCO3 will react to reach equilibrium?

4. The equilibrium constant is 0.0900 at 25°C for the reaction H2O(g) + Cl2O(g) ↔ 2HOCl(g)

For which of the following sets of conditions is the system at equilibrium? For those which are not at equilibrium, in which direction will the system shift?

a. A 1.0-L flask contains 1.0 mol HOC1, 0.10 mol C12O, and0.10molH2O.

b. A 2.0-L flask contains 0.084 mol HOC1, 0.080 mol C12O,and 0.98 mol H2O.

c. A 3.0-L flask contains 0.25 mol HOC1, 0.0010 mol C12O,and 0.56 mol H2O.

5. The equilibrium constant is 0.0900 at 25°C for the reaction H2O(g) + Cl2O(g)↔ 2HOCl(g)

For which of the following sets of conditions is the system at equilibrium? For those which are not at equilibrium, in which direction will the system shift? (note : Kp will be unitless, so any units can be used to calc. Q).

a. PH2O = 1.00 atm, PCl2O= 1.00 atm, PHOCl = 1.00 atm

b. PH2O= 200. torr, PCl2O = 49.8 torr, PHOCl= 21.0 torr

c. PH2O = 296 torr, PCl2O = 15.0 torr, PHOCl= 20.0 torr

6. At 900°C, Kp = 1.04 atm for the reaction CaCO3(s) ↔ CaO(s) + CO2(g)

At a low temperature, dry ice (solid CO2), calcium oxide, and calcium carbonate are introduced into a 50.0-L reaction chamber. The temperature is raised to 900°C, resulting in the dry ice converting to gaseous CO2. For the following mixtures, will the initial amount of calcium oxide increase, decrease, or remain the same as the system moves toward equilibrium at 900°C?

a. 655 g CaCO3, 95.0 g CaO, PCO2 = 2.55 atm

b. 780 g CaCO3, 1.00 g CaO, PCO2 = 1.04 atm

c. 0.14 g CaCO3, 5000 g CaO, PCO2 = 1.04 atm

d. 715 g CaCO3, 813 g CaO, PCO2= 0.211 atm

7.Ethyl acetate is synthesized in a nonreacting solvent (not water) according to the following reaction:

CH3CO2H + C2H5OH ↔ CH3CO2C2H5 + H2O K = 2.2

Acetic acid Ethanol Ethyl acetate

For the following mixtures (a-d), will the concentration of H2O increase, decrease, or remain the same as equilibrium is established?

a. [CH3CO2C2H5] = 0.22 M, [H2O] = 0.10M, [CH3CO2H] =0.010 M, [C2H5OH] = 0.010 M

b. [CH3CO2C2H5] = 0.22 M, [H2O] = 0.0020 M, [CH3CO2H] =0.0020 M, [C2H5OH] = 0.10 M

c. [CH3CO2C2H5] = 0.88 M, [H2O] = 0.12M, [CH3CO2H] =0.044 M, [C2H5OH] = 6.0 M

d. [CH3CO2C2H5] = 4.4 M, [H2O] = 4.4 M, [CH3CO2H] =0.88 M, [C2H5OH] = 10.0 M

e. What must the concentration of water be for a mixture with[CH3CO2C2H5] = 2.0 M, [CH3CO2H] = 0.10M, [C2H5OH] =5.0 M to be at equilibrium?

f. Why is water included in the equilibrium expression forthis reaction?

8.`The equilibrium constant for the reaction H2(g) + F2(g) ↔ 2HF(g) has the value 2.1 x 103 at a particular temperature. When the system is analyzed at equilibrium at this temperature, the concentrations of H2(g) and F2(g) are both found to be 0.0021 M. What is the concentration of HF(g) in the equilibrium system under these conditions?

9. A 1.00-L flask was filled with 2.00 mol gaseous SO2 and 2.00 mol gaseous NO2 and heated. After equilibrium was reached,it was found that 1.30 mol gaseous NO was present. Assumethat the reaction SO2(g) + NO2(g) ↔ SO3(g) + NO(g) occurs under these conditions. Calculate the value of the equilibrium constant for this reaction.

10.At a particular temperature, 8.0 mol NO2 is placed into a 1 .0-L container and the NO2 dissociates by the reaction 2NO2(g) ↔ 2NO(g) + O2(g) At equilibrium the concentration of NO(g) is 2.0 M. Calculate

K for this reaction.

11. At a particular temperature, K = 2.50 for the reaction SO2(g) + NO2(g) ↔ SO3(g) + NO(g). If all four gases had initial concentrations of 1.00 M, what are the equilibrium concentrations of these gases?

12. At 2200 ºC, Kp = 0.050 for the reaction N2(g) + O2(g) ↔ 2 NO(g). What is the partial pressure of NO in equilibrium with N2 and O2 that were placed in the flask at initial pressures of 0.80 and 0.20 respectively?

13. For the reaction N2O4(g) ↔ 2NO2(g), Kp = 0.25 atm at a certain temperature. What are the equilibrium partial pressures of NO2 and N2O4 for each of the following initial conditions?

a. Pure NO2 at a pressure of 0.050 atm

b. Pure N2O4 at a pressure of 0.040 atm

c. A mixture with PN2O4= PNO2 = 1.00 atm

14. At a particular temperature, K = 2.0 x 10-6 mol/L for the reaction 2CO2(g)↔ 2CO(g) + O2(g). If 2.0 mol CO2 is initially placed in a 5.0 L vessel, calculate the equilibrium concentrations of all species.

15. A sample of solid ammonium chloride was placed in an evacuated container and then heated so that it decomposed to ammonia gas and hydrogen chloride gas. After heating, the partial pressure of NH3 in the container was found to be 2.2 atm. Calculate Kpat this temperature for the decomposition reaction

NH4Cl(s) ↔ NH3(g) + HCl(g)

Answers : 3. 84.1% 4a. Q = 1.0 x 102 > K, shift left 4b. at equil. 4c. left 5a. Q=1.00>K, left 5b. right 5c. about at equil. 6a. 2.55>K, left 6b. at eq. 6c. at eq. 6d. right 7a. Q = 220, left 7b. at eq. 7c. right 7d. at eq. 7e. [H2O] = 0.55 M 7f. water is a product, and not just the solvent or medium in which the reaction occurs 8. [HF] = 0.096 M 9. K = 3.4 10. K = 0.11 mol/L 11. [SO3] and [NO] = 1.22 M, [SO2] and [NO2] = 0.78 M 12. PNO = 7.8 x 10-2 atm 13a. PN2O4 = 5.9 x 10-3 atm, PNO2 = 3.8 x 10-2 atm 13b. PN2O4 = 0.012atm, PNO2 = 0.056 atm 13c. PN2O4 = 1.22 atm, PNO2 = 0.56 atm 14a. [CO2] = 0.39 M, [CO] = 8.6 x 10-3 M, [O2] = 4.3 x 10-3 M 15. Kp = 4.8 atm2

Ws-13-4-10