Unit 13 Review

1. Given the equilibrium equation at 25oC:        A2 (g) + B2 (g)        2 AB (g)

     If, at equilibrium, the concentrations are as follows:  [A2] = 3.45 M, [B2] = 5.67 M, and
    [AB] = 0.67 M

(A) Write the Keq expression for the reaction.    Keq =   [AB]2    
                                                                                      [A2][B2]

(B) Find the value of the equilibrium constant at 25oC.          0.023

 

2. Given the equilibrium equation:         X2 (g) + 3 Y2 (g)        2 XY3 (g)           at a temperature
    of 50
°C, it is found that when equilibrium is reached that:
          [X
2] = 0.37 M, [Y2] = 0.53 M and [XY3] = 0.090 M

          (A) Write the equilibrium constant expression (Keq).             Keq =   [XY3]2   

                                                                                                          [X2][Y2]3

(B) Calculate the value of Keq at 50°C.             0.15

 

3. Predict which way these equilibrium systems will shift when the total pressure is increased.

(A) N2 (g) + O2 (g)         2 NO (g)                 no shift

(B) 2 SO2 (g) + O2 (g)        2 SO3 (g)            right

(C) 4 NH3 (g) + 5 O2 (g)         4 NO (g) + 6 H2O (g)          left

 

4. Hydrogen peroxide decomposes according to the following equation:

187 kJ + H2O2 (l)        H2 (g) + O2 (g)

Predict the direction of equilibrium shift by each of these changes:

(A) Increase the [H2] left                                (B) Decrease the [O2right

(C) Decrease the total pressure right               (D) Increase the temperature  right

 

5. Consider the following equilibrium and answer the questions when these changes are made.

Heat + CH4 (g) + 2 H2S (g)         CS2 (g) + 4 H2 (g)

~ CH4 gas is added           (A) direction of equilibrium shift?  right
                                                (B) [H2S]?  decreases

                                      (C) [CS2]?  increases

                                      (D) [H2]?  increases

~ CS2 gas is removed        (A) direction of equilibrium shift?  right
                                                (B) [CH4]?  decreases

                                      (C) [H2S]?  decreases

                                      (D) [H2]?  increases
~ H
2 gas is added             (A) direction of equilibrium shift?  left
                                      (B) [CH4]?  increases

                                      (C) [H2S]?  increases

                                      (D) [CS2]?  decreases

~ The temperature is increased    (A) direction of equilibrium shift?  right
                                                (B) [CH4]?  decreases

                                                (C) [H2S]?  decreases

                                                (D) [CS2]?  increases
                                                          (E) [H2]?  increases