Question

The $pH$ of a solution of $N{H}_{4}Cl$ is 4.86. calculate the molar concentration of the solution if $K_b=1.0\times {10}^{-5}$ and $K_w=1.0\times {10}^{-14}$.

Answer 1

$N{H}_{4}Cl:$ Acide salt

$pH=4.86;K_b={10}^{-5}$

$\because$ we know for an acidic salt

$pH=7-\frac{1}{2}(P^{K_b}+\log c)$

$\Rightarrow 4.86=7-\frac{1}{2}(-\log ({10}^{-5})+\log c)$

$\Rightarrow 4.28=5+\log c$

$\Rightarrow c=0.19$

$\Rightarrow \left[N{H}_{4}Cl\right]=0.19M$