Workshop CHE 168
Problem Set #5
 
 

1.

(a) A mixture of hydrogen and nitrogen in a reaction vessel is allowed to attain equilibrium at 472 ^oC. The equilibrium mixture of gases was analyzed and found to contain 0/1207 M H₂, 0.0402 M N₂, and 0.00272 M NH₃. From these data, calculate the equilibrium constant, K_c, for N_{2 (g)} + 3 H_{2 (g)}  2 NH_{3 (g)}.

(b) What is K_p for this reaction at this temperature?

2. Sulfur trioxide decomposes at high temperature in a sealed container:

2 SO_{3 (g)}  2 SO_{2 (g)} + O_{2 (g)}.
 

(a) Initially the vessel is charged at 1000 K with SO_{3 (g)} at a concentration of 6.09 x 10^-3 M. At equilibrium, the SO₃ concentration is 2.44 x 10^-3 M. Calculate the value of K_c.
(b) Calculate the value for K_p for this reaction.
(c) Calculate the value for Q_c and predict the direction in which the reaction will proceed toward at equilibrium if the initial concentrations of reactants at 1000 K are [SO₃] = 2 x 10^-3 M; [SO₂] = 5 x 10^-3 M; [O₂] = 3 x 10^-2 M.

3. At 500 K, the equilibrium constant K_p for the reaction

PCl_{5 (g)}  PCl_{3 (g)} + Cl_{2 (g)}

has the value 0.497. In an equilibrium mixture at this temperature, the partial pressure of PCl₅ is 0.860 atm and that of PCl₃ is 0.350 atm. What is the partial pressure of Cl₂ in the equilibrium mixture?

4. Given:

N_{2 (g)} + 3 H_{2 (g)}  2 NH_{3 (g)} K_c = 0.105 @ 472 ^oC

A 2.00 L flask is filled with 0.500 mol of NH₃ and is allowed to reach equilibrium. What are the equilibrium concentrations of NH₃, N₂ and H₂?

5. Given:

H_{2 (g)} + I_{2 (g)}  2 HI _(g) K_c = 50.5 @ 448 ^oC

A 1.00-L flask is filled with 0.500 mol of HI. Determine the concentrations of H₂, I₂ and HI at equilibrium.

6. Given:

N₂O_{4 (g)}  2 NO_{2 (g)} K_c = 4.61 x 10- ³ @ 25 ^oC

A 0.0240 mol sample of N₂O₄ is placed in a 0.372-L flask and allowed to equilibrate. Calculate (a) the amount in moles of N₂O₄ present at equilibrium, (b) the amount in moles of NO₂ present at equilibrium, and (c) the percent dissociation of the N₂O₄.

7. Given:

N₂O_{4 (g)}  2 NO_{2 (g)} DH = +58.0 kJ @ 25 ^oC

In what direction will the equilibrium shift when each of the following changes is made to a system at equilibrium? (a) Add N₂O₄; (b) remove NO₂; (c) increase the volume; (d) decrease the temperature?

8. Given:

PCl_{5 (g)}  PCl_{3 (g)} + Cl_{2 (g)} D H = +87.9 kJ @ 25 ^oC

In what direction will the equilibrium shift when
 

(a) Cl_{2 (g)} is added
(b) the temperature is increased
(c) the volume of the reaction system is decreased
(d) PCl_{5 (g)} is added?

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