Chapter 13. Chemical Equilibrium
EndofChapter Material
Additional Exercises
 What is the relationship between the K_{sp} expressions for a chemical reaction and its reverse chemical reaction?
 What is the relationship between the K_{w} value for H_{2}O and its reverse chemical reaction?
 For the equilibrium
PCl_{3}(g) + Cl_{2}(g) ⇄ PCl_{5}(g) + 60 kJ
list four stresses that serve to increase the amount of PCl_{5}.
 For the equilibrium
N_{2}O_{4} + 57 kJ ⇄ 2NO_{2}
list four stresses that serve to increase the amount of NO_{2}.
 Does a very large K_{eq} favour the reactants or the products? Explain your answer.
 Is the K_{eq} for reactions that favour reactants large or small? Explain your answer.
 Show that K_{a} × K_{b} = K_{w} by determining the expressions for these two reactions and multiplying them together.
HX(aq) ⇄ H^{+}(aq) + X^{–}(aq)
X^{–}(aq) + H_{2}O(ℓ) ⇄ HX(aq) + OH^{–}(aq)  Is the conjugate base of a strong acid weak or strong? Explain your answer.
 What is the solubility in moles per litre of AgCl? Use data from Table 13.2 “Solubility Product Constants for Slightly Soluble Ionic Compounds”.
 What is the solubility in moles per litre of Ca(OH)_{2}? Use data from Table 13.2.
 Under what conditions is K_{eq} = K_{P}?
 Under what conditions is K_{eq} > K_{P} when the temperature is 298 K?
 What is the pH of a saturated solution of Mg(OH)_{2}? Use data from Table 13.2.
 What are the pH and the pOH of a saturated solution of Fe(OH)_{3}? The K_{sp} of Fe(OH)_{3} is 2.8 × 10^{−39}.
 For a salt that has the general formula MX, an ICE chart shows that the K_{sp} is equal to x^{2}, where x is the concentration of the cation. What is the appropriate formula for the K_{sp} of a salt that has a general formula of MX_{2}?
 Referring to Exercise 15, what is the appropriate formula for the K_{sp} of a salt that has a general formula of M_{2}X_{3} if the concentration of the cation is defined as 2x, rather than x?
 Consider a saturated solution of PbBr_{2}(s). If [Pb^{2+}] is 1.33 × 10^{−5} M, find each of the following.
 [Br−]
 the K_{sp} of PbBr_{2}(s)
 Consider a saturated solution of Pb_{3}(PO_{4})_{2}(s). If [Pb^{2+}] is 7.34 × 10^{−14} M, find each of the following.
 [PO_{4}^{3−}]
 the K_{sp} of Pb_{3}(PO_{4})_{2}(s)
Answers
 They are reciprocals of each other.
 increase the pressure; decrease the temperature; add PCl_{3}; add Cl_{2}; remove PCl_{5}
 favour products because the numerator of the ratio for the Keq is larger than the denominator
 1.3 × 10^{−5} mol/L
 K_{eq} = K_{P} when the number of moles of gas on both sides of the reaction is the same.
 10.35
 4x^{3}

 2.66 × 10^{−5} M
 9.41 × 10^{−15}