Part A

Suppose you wanted to make a buffer of exactly $pH7\mathrm{.}00$ using $K{H}_{2}P{O}_4$ and

$N{a}_{2}HP{O}_4.$ If the final solution was $0\mathrm{.}14M$ in $K{H}_{2}P{O}_4,$ what concentration of

$N{a}_{2}HP{O}_4$ would you need? $(p{K}_a$ for $H_{3}P{O}_4,H_{2}P{O}_4^{-},$ and $HP{O}_4^{2-}$ are

$2\mathrm{.}14,6\mathrm{.}86,$ and $12\mathrm{.}40,$ respectively.$)$

Express your answer to two significant figures.