1. Write equilibrium (mass action) expressions for each of the following reactions:
(a) H2(g) + I2(g) 2 HI
(b)2 NO(g) + O2(g) 2 NO2(g)
(c)N2(g) + 3 H2(g) 2 NH3(g)
(d) CO(g) + NO2(g) CO2(g) + NO(g)
(e) 2 CO(g) + O2(g) 2 CO2(g)
2. Write equilibrium expressions for each of the following equilibria:
(a) 2 C(s) + O2(g) CO(g)
(b) Zn2+(aq) + H2S(g) ZnS(s) + 2 H+(aq)
(c) HCl(g) + H2O() H3O+(aq) + Cl–(aq)
(d)H2(g) + O2(g) H2O(g)
3. Which of the following is more likely to precipitate the hydroxide ion?
(a) Cu(OH)2(s) Cu2+(aq) + 2 OH–(aq) K= 1.6 ´10–20
(b)Ca(OH)2(s) Ca2+(aq) + 2 OH–(aq) K= 7.9 ´10–6
4. The reaction, 3 H2(g) + N2(g) 2 NH3(g), has the following equilibrium constants at the temperatures given:
atT= 25°C, K= 2.8 ´104
at T= 500°C, K= 2.4 ´10–7
(a) At which temperature are reactants favored?
(b)At which temperature are products favored?
5. Consider the following equilibria involving SO2(g) and their corresponding equilibrium constants:
SO2(g) + O2(g) SO3(g) K1
2 SO3(g) 2 SO2(g) + O2(g) K2
Which of the following expressions relates K1to K2?
(b) K22= K1
(e) K2= 1/K12
6. The following data were collected for the reaction, H2(g) + I2(g) 2 HI(g), at equilibrium at 25°C.
[H2] = 0.10 mol L–1, [I2] = 0.20 mol L–1, [HI] = 4.0 mol L–1
Calculate the equilibrium constant for the reaction at this temperature.
7. The equilibrium constant for the reaction, 3 H2(g) + N2(g) 2 NH3(g), at a given temperature is 1.4 ´10–7. Calculate the equilibrium concentration of ammonia, if [H2] = 1.2 ´10–2mol L–1and [N2] = 3.2 ´10–3mol L–1.
8. Hydrogen gas and iodine gas react via the following equation:
H2(g) + I2(g) 2 HI(g) Kc= 76 (at 600 K)
If 0.050 mol HI is placed in an empty 1.0-L flask at 600 K, what are the equilibrium concentrations of HI, I2, and H2?
9. The equilibrium constant of the reaction of Cl2(g) with PCl3(g) to produce PCl5(g) is 51 at a particular temperature. If the initial concentration of PCl3is 0.012 mol L–1 and the initial concentration of Cl2is 0.125 mol L–1, what are the equilibrium concentrations of all species?
10. At a particular temperature, the equilibrium constant, K, for the dissociation of N2O4into NO2is 133. If the initial concentration of N2O4is 0.100 mol L–1, what are the concentrations of all species at equilibrium?
N2O4 2 NO2
Answer 2 and 3
When Kc is more than 1 then products are favored at equilibrium.
a) At 500 o C, Kc is less than 1, so reactants are favored.
b) At 25 oC, Kc is more than 1, so products are favored.
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