Assignment
1. Among the solubility rules previously discussed is the statement: Carbonates, phosphates, borates, and arsenates-except those of the ammonium ion and the alkali metals-are insoluble. (a) Write the expression for the equilibrium constant for the reaction represented by the equation CaCO3(s) ? Ca2+(aq) + CO3 -(aq). Is Kc > 1, < 1, or ≈ 1? Explain your answer. (b) Write the expression for the equilibrium constant for the reaction represented by the equation 3Ba2+(aq) + 2PO4 3-(aq) ? Ba3 (PO4)2(s). Is Kc > 1, < 1, or ≈ 1? Explain your answer.
2. Write the mathematical expression for the reaction quotient, Qc, for each of the following reactions:
(a) N2(g) + 3H2(g) ? 2NH3(g)
b) 4NH3(g) + 5O2(g) ? 4NO(g) + 6H2 O(g)
c) N2 O4(g) ? 2NO2(g)
D) CO2(g) + H2(g) ? CO(g) + H2 O(g)
e) NH4 Cl(s) ? NH3(g) + HCl(g)
f) 2Pb??NO3??2(s) ? 2PbO(s) + 4NO2(g) + O2(g)
g) 2H2(g) + O2(g) ? 2H2 O(l)
h) S8(g) ? 8S(g)
4.Write the expression of the reaction quotient for the ionization of HOCN in water.
5. Suggest four ways in which the concentration of PH3 could be increased in an equilibrium described by the following equation: P4(g) + 6H2(g) ? 4PH3(g) ΔH = 110.5 kJ
6. Pure iron metal can be produced by the reduction of iron(III) oxide with hydrogen gas.
a) Write the expression for the equilibrium constant (Kc) for the reversible reaction Fe2 O3(s) + 3H2(g) ? 2Fe(s) + 3H2 O(g) ΔH = 98.7 kJ
b) What will happen to the concentration of each reactant and product at equilibrium if more Fe is added?
c) What will happen to the concentration of each reactant and product at equilibrium if H2O is removed?
d) What will happen to the concentration of each reactant and product at equilibrium if H2 is added?
e) What will happen to the concentration of each reactant and product at equilibrium if the pressure on the system is increased by reducing the volume of the reaction vessel? (f) What will happen to the concentration of each reactant and product at equilibrium if the temperature of the system is increased?
7. Hydrogen is prepared commercially by the reaction of methane and water vapor at elevated temperatures. CH4(g) + H2 O(g) ? 3H2(g) + CO(g) What is the equilibrium constant for the reaction if a mixture at equilibrium contains gases with the following concentrations: CH4, 0.126 M; H2O, 0.242 M; CO, 0.126 M; H2 1.15 M, at a temperature of 760 °C?
8. Calculate the number of moles of HI that are at equilibrium with 1.25 mol of H2 and 1.25 mol of I2 in a 5.00-L flask at 448 °C. H2 +I2 ? 2HI Kc = 50.2at448°C
9. A student solved the following problem and found [N2O4] = 0.16 M at equilibrium. How could this student recognize that the answer was wrong without reworking the problem? The problem was: What is the equilibrium concentration of N2O4 in a mixture formed from a sample of NO2 with a concentration of 0.10 M? 2NO2(g) ? N2 O4(g) Kc = 160.