Question 21.1: For the reaction Cl2(g) + H2O EF Cl-(aq) + H+(aq) + HClO(aq)...
For the reaction Cl_{2}(g) + H_{2}O \rightleftharpoons Cl^{-}(aq) + H^{+}(aq) + HClO(aq),
(a) write the expression for the equilibrium constant K.
(b) given that K = 2.7 × 10^{-5} , calculate the concentration of HClO in equilibrium with Cl_{2}(g) at 1.0 atm.
| ANALYSIS | |
| reaction: (Cl_{2}(g) + H_{2}O \rightleftharpoons Cl^{-}(aq) + HClO(aq) + H^{+}(aq)) P_{Cl_{2}}(1.0 atm) K(2.7 × 10^{-5}) |
Information given: |
| (a) K expression (b) [HClO] |
Asked for: |
STRATEGY
(a) 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) 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.
| K = \frac{[HClO][Cl^{-}][H^{+}]}{P_{Cl_{2}}}
2.7 × 10^{-5} = \frac{(x)(x)(x)}{1.0} → x³ = 2.7 × 10^{-5} → x = 0.030 M |
(a) K expression
(b) [HClO] |