Question

A solution of ammonia bought for cleaning the windows was found to be $10$% ammonia by mass, having a density of $0.935g.m{L}^{-1}$. What is the $pH$ of the solution. Take $K_b$ for protonation of ammonia$=5.5\times {10}^{-6}$.

Answer 1

$C=\frac{10\times 0.935\times 1000}{17\times 100}=5.5M$
$K_a=C{\alpha }^2$ $\Rightarrow$ $5.5\times {10}^{-6}=5.5{\alpha }^2$
$\alpha ={10}^{-3}$
$\left[{OH}^{-}\right]=C\alpha =C\alpha =5.5\times {10}^{-3}$
$pOH=2.26$, $pH=11.74$