AP Chemistry Chapter 13 Section 1-6 Equilibrium Expression and Constant

AP Chemistry Chapter 13 Section 1-6 Equilibrium Expression and Constant

1.  Given : 2CO2(g) Û 2CO(g) + O2(g); Keq = 26

2NH3(g) Û N2(g) + 3H2(g); Keq = 5.0 x 10+4

Determine the equilibrium constant at the same temperature, for:

CO2(g) Û CO(g) + ½ O2(g); Keq = ______

N2(g) + 3H2(g) Û 2NH3(g); Keq = ______

2.  The commercial preparation of methanol, CH3OH, is done at elevated temperatures with the reaction:

CO(g) + 2H2(g) Û CH3OH(g)

At a certain temperature, the Keq value is 7.3. Will the system be at equilibrium with the following initial concentrations? If not, in which direction will the system shift to achieve equilibrium? Show work.

a.  0.80M CO and 1.5M H2

b.  a gaseous mixture of 0.90 mol CH3OH, 0.45mol CO, and 0.45mol H2in a 3.0L container.

3. For the reaction: Br2(g) Û 2Br(g); Keq = 4.0 x 10-18mol/L at 200.0 °C. If one starts with 2.00mol Br2 in a 2.00L container, will the equilibrium contain: a. mostly Br2 b. mostly Br atoms c. about equal amounts of both?

4.  When 0.250 mol of CO2 is placed in a one liter container, some of it decomposes by the reaction: 2CO2(g) Û 2CO(g) + O2(g) The equilibrium concentration of CO is 0.050 mol/L. Calculate K.

5.  For the system: PCl5(g) ↔ PCl3(g) + Cl2(g) K = 0.050 at 250°C. If 0.40 mol of PCl5 is placed in a one

liter container at this temperature calculate the equilibrium concentration of all species.

6. The equilibrium constant for the reaction: H2(g) + F(g) Û 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 0.0021M. What is the concentration of HF(g) in this equilibrium?

7. At a particular temperature, K = 2.50 for the reaction: SO2(g) + NO2(g) Û SO3(g) + NO(g).

If all four gases had initial concentrations of 1.00M, calculate the equilibrium concentrations of the gases.

8. A sample of S8(s) is placed in an otherwise empty rigid container at 1325K at an initial pressure of 1.00 atm, where it decomposes to S2(g) by the reaction:

S8(g) ↔ 4S2(g)

At equilibrium, the partial pressure of S8(g) is 0.25 atm. Calculate the Kp for this reaction at 1325K.

9. At 25˚C, K = 0.090 for the reaction: H2O(g) + Cl2O(g) ↔ 2HOCl(g).

a.  Calculate the Kp for this reaction.

b.  Find the concentrations of all species at equilibrium as 1.0 mol pure HOCl is placed in a 2.0-liter flask.

10. Lexan is a plastic used to make compact discs eyeglass lenses and bullet-proof glass. One of the compounds used to make Lexan is phosgene, COCl2, an extremely poisonous gas. Phosgene decomposes by the reaction: COCl2(g) ↔ CO(g) + Cl2(g)

For which the Kp = 6.8 x 10-9 at 100˚C. If pure phosgene at an initial pressure of 1.0 atm decomposes, calculate the equilibrium pressures of all species.

11. For the Haber process, N2(g) + 3H2(g) ↔ 2NH3(g), Kp = 1.45 x 10-5 at 500°C. In an equilibrium mixture of the three gases at 500°C, the partial pressure of H2 = 0.928 atm. and that of N2 = 0.432 atm. What is the partial pressure of NH3 in this equilibrium?