A 0.10 M $\mathrm{Na}{}_2\mathrm{CO}{}_3$ solution at 298 K is analysed using $K_{a1}=4.3\times 10^{-7}$ and $K_{a2}=4.7\times 10^{-11}$ for $\mathrm{H}{}_2\mathrm{CO}{}_3$. Take $[\mathrm{OH}{}^{-}]=\sqrt{K_{h1}c}$ and neglect the second hydrolysis for the pH. Select the correct statements.

1. AThe pH lies between 11.6 and 11.7
2. B$[\mathrm{HCO}{}_3{}^{-}]\approx [\mathrm{OH}{}^{-}]$
3. C$[\mathrm{H}{}_2\mathrm{CO}{}_3]\approx K_w/K_{a1}=2.3\times 10^{-8}$ M
4. DThe second hydrolysis step contributes more $\mathrm{OH}{}^{-}$ than the first