Question 21.1: Consider the reaction between chlorine gas and water. Cl2(g)...
Consider the reaction between chlorine gas and water.
Cl_{2}(g) + H_{2}O \rightleftharpoons Cl^-(aq) + H^+(aq) + HClO(aq)
a Write the expression for the equilibrium constant K.
STRATEGY
Recall that in the K expression
■ gases enter as partial pressures in atmospheres.
■ aqueous species enter as concentrations in molarity.
■ water is not included.
■ products are written in the numerator raised to their coefficient in the balanced equation.
■ reactants are written in the denominator raised to their coefficient in the balanced equation.
b At the temperature of the reaction, K = 2.7 \times 10^{-5}. What is the concentration of HClO in equilibrium with chlorine gas at 1.0 atm?
ANALYSIS
Information given: P_{Cl_{2}}(1.0 atm), K( 2.7 \times 10^{-5})
Information implied: from (a) K expression
Asked for: [HClO]
STRATEGY
Substitute into the K expression obtained in (a).
Let x = [HClO]
Note that the stoichiometric ratios of HClO, H^+, and Cl^- are 1:1:1, thus [HClO] = [H^+] = [Cl^-] = x
