Carbon dioxide dissolves in pure water and establishes the sequential equilibria A…

CHEMISTRY · Single correct · AP · Chemistry · Acids and Bases · Acids and Bases

Problem

Carbon dioxide dissolves in pure water and establishes the sequential equilibria

\text{CO}_2(aq)+\text{H}_2\text{O}(l) \;\rightleftharpoons\; \text{H}^+(aq)+\text{HCO}_3^{-}(aq)

K_{a1}=4.3\times10^{-7}

\text{HCO}_3^{-}(aq) \;\rightleftharpoons\; \text{H}^+(aq)+\text{CO}_3^{2-}(aq)

K_{a2}=5.6\times10^{-11}

A sample of water at 25 °C is saturated with CO

_2

so that

[\text{CO}_2(aq)]=0.033\;\text{M}

. Neglecting the auto-ionization of water, what is the equilibrium concentration of CO

_3^{2-}(aq)

? (a)

6.2\times10^{-8}\;\text{M}

(b)

5.6\times10^{-11}\;\text{M}

(c)

1.2\times10^{-4}\;\text{M}

(d)

4.3\times10^{-7}\;\text{M}