# 0.10 mol of solid sodium hydrogen carbonate and 0.20 mol of solid sodium carbonate are dissolved in the same beaker of water, transferred to a volumetric ﬂask and made to 250.0 mL. The Ka for HCO3 - is 4.7 x 10-11. What is the pH of the resulting buﬀer?

$p H = p {K}_{a} + {\log}_{10} \left(\frac{{A}^{-}}{H A}\right) = - {\log}_{10} \left(4.7 \times {10}^{- 11}\right) + {\log}_{10} \left(\frac{0.2}{0.1}\right)$
$p H = 10.3 + 0.3 = 10.6$