Blood is buffered with ${\mathrm{CO}}_2$ and ${\mathrm{HCO}}_3^{-}$. What is the ratio of the base concentration to the acid (i.e., ${\mathrm{CO}}_2\left(aq\right)\text{ plus }{\mathrm{H}}_2{\mathrm{CO}}_3\text{ ) }$concentration to maintain the pH of blood at 7.4? The first dissociation constant of

${\mathrm{H}}_2{\mathrm{CO}}_3\left({\mathrm{H}}_2{\mathrm{CO}}_3\rightleftharpoons {\mathrm{H}}^{+}+{\mathrm{HCO}}_3^{-}\right)$ is $4.2\times {10}^{-7}$ where the ${\mathrm{H}}_2{\mathrm{CO}}_3$ is assumed to include ${\mathrm{CO}}_2\left(aq\right)$ i.e., dissolved ${\mathrm{CO}}_2\cdot [\log 4.2=0.6232]$