Answer
a) $1.51\times 10^{-4}$M
b) $3.02\times 10^{-7}$M
c) $7.76\times 10^{-12}$M
Work Step by Step
pH = -$log_{10}[H]$
Rearranging, [H] = $10^{-pH}$
a) [H] = $10^{-3.82}$ =$1.51\times 10^{-4}$M
b) [H] = $10^{-6.52}$ =$3.02\times 10^{-7}$M
c) [H] = $10^{-11.11}$ = $7.76\times 10^{-12}$M