Chapter 16 End-of-Chapter Problems

From UCDavis Chemwiki

1.Write the equilibrium constant expression for each of the following reactions:

`1. 2SO_2 (g) + O_2 (g) ? 2SO_3 (g)`

`2. N_2 O(g) + 1/2 O_2 (g) ? 2NO_ (g)`

`3. Cu (s) + 2Ag^(+) (aq) ? Cu^(2+) (aq) + Ag(s)`

`4. CaCO_3 (g) ? CaCO(s) + CO_2 (g)`

`5. 2NaHCO_3 (s) ? Na_2 CO_3 (s) + CO_2 (g) + H_2O (g)`

 

2. What is the `K_c` of the following reaction?

`2SO_2 (g) + O_2 (g) ? 2SO_3 (g)`

with concentration `SO_2 (g) = 0.2MO_2 (g) = 0.5MSO_3 (g) = 0.7M`

Also, what is the `K_p` of this reaction? At room temperature?

 

3.For the same reaction, the differing concentrations:

`SO_2 (g) = 0.1MO_2 (g) = 0.3MSO_3 (g) = 0.5M`

Would this go towards to product or reactant?

 

4.Write the Partial Pressure Equilibrium expression for the following reaction:

`C(s) + O_2 (g) -> CO_2 (g)`

 

5. Write the reaction for this Partial Pressure:

`K_p = (P_(HI)^2)/(P_(H_2) * P_(I_2))`
 

6. You are given the following chemical equation and its equilibrium constant at a given temperature.

`2HBr(g) + Cl_2(g) -> 2HCl(g) +Br_2(g)`                       `K_c = 4.0 x 10^4`

 

Write the expression for, and calculate the numerical value of, the equilibrium constant for each of the following at the same temperature.

a)      `4HBr(g) + 2Cl_2(g) -> 4HCl(g) + 2Br_2(g)`

b)      `HBr(g) + 1/2 Cl_2(g) -> HCl(g) + 1/2 Br_2­(g)`

 

7. Fill in this ICE table:

Reaction:	[HA]	[A-]	[H3O+]
Initial Amount	0.650 mol	?	?
Change in Amounts	?	?	?
Equilibrium Amount	0.250 mol	?	?

 

8. What will happen to the equilibrium when more `2SO_2 (g)` is added to the system?

`2SO_2 (g) + O_2 (g) ? 2SO_3 (g)`

 

9. What will happen to the equilibrium when the volume of the system is decreased?

`2SO_2 (g) + O_2 (g) ? 2SO_3 (g)`

 

10. What wikk happen ti the equilibrium when the temperature of the system is decreased?

`N_2 (g) + O_2 (g) ? 2NO (g)`     `DeltaH = 180.5`kj

 

11. Given K = 2.81x10^-16 for the following reaction Cu²⁺_(aq) + Ag_(s)  ? Cu_(s) + 2Ag^+,  find `DeltaG`.

 

12. Write an equilibrium expression for each chemical equation (Careful, some contain liquids and solids).

a. `SbCl_5 (g) -> SbCl_3 (g) + Cl_2 (g)`

b. `2BrNO(g) -> 2NO (g) + Br_2 (g)`

c. `CO_3^(2-) (aq) + H_2O(l) -> HCO_3^(-) (aq) + OH^(-) (aq)`

d. `2KClO_3(s) -> 2KCl(s) + 3O_2(g)`

 

13. Consider the reaction:  `NH_4HS(s) -> NH_3(g) + H_2S(g)`

a. An equilibrium mixture of this reaction at 27 degrees celsius was found to have [NH₃] = 0.278 M and [H₂S] = 0.355 M. What is the value of the equilibrium constant (K_c) at this temperature?

b. Convert your K_c to K_p.

 

14. Consider the reaction:

`HC_2 H_3 O_2(aq) + H_2O(l) -> H_3 O^(+)(aq) + C_2 H_3 O_2^(-) (aq)`    `K_c=1.8x10^(-5) at 25°C.`

If the solution initially contains 0.210 M HC₂H₃O₂, what is the equilibrium concentration of H₃O⁺ at 25°C?

15. Consider the reaction `NH_4HS(s) -> NH_3(g) + H_2S(g)`

At a certain temperature, K_c = 8.5x10^-3. A reaction mixture at this temperature containing solid NH₄HS has [NH₃] = 0.166 M and [H₂S] 0.166 M. Will more of the solid form or will some of the existing solid decompose as equilibrium is reached?

16. Consider the reaction at equilibrium: `2KClO_3(s) -> 2KCl(s) + 3O_2(g)`

Predict whether the reaction will shift left, shift right, or remain unchanged upon each disturbance.

a.       O­₂ is removed from the reaction mixture.

b.      KCl is added to the reaction mixture.

c.       KClO₃ is added to the reaction mixture.

d.      O₂ is added to the reaction mixture.

17. In the water–gas shift reaction introduced in Example 10, carbon monoxide produced by steam-reforming reaction of methane reacts with steam at elevated temperatures to produce more hydrogen:

`CO (g) + H_2O(g) ? CO_2 (g) + H_2 (g)`

K = 0.64 at 900 K. If 0.010 mol of both CO and H₂O, 0.0080 mol of CO₂, and 0.012 mol of H₂ are injected into a 4.0 L reactor and heated to 900 K, will the reaction proceed to the left or to the right as written? (Hint: you will need the reaction quotient for this problem)

18. For each equilibrium system, predict the effect of the indicated stress on the specified quantity.

a. `2SO_2 (g) + O_2 (g) ? 2SO_3 (g)` : (1) the effectof removing `O_2` on `P_(SO_(2))`; the effect of removing `O_2` on `P_(SO_(3))`.

b. `CaCO_3 (s) `P_(SO_(2))` CaO(s) + CO_2 (g)`: (1) the effect of removing `CO_2` on the amount of `CaCO_3`; (2) the effect of adding `CaCO_3` on `P_(SO_(2))`.

19. For each equilibrium reaction, predict the effect of decreasing the temperature:

a. `N_2 (g) + 3H_2 (g) ? 2NH_3 (g)`     `DeltaH_"rxn" = -91.8`kJ/mol.

b. `CaCO_3 (s) ? CaO (s) + CO_2 (g)`     `DeltaH_"rxn" = 178`kj/mol.

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