Question

A solution has $pH=5$. It is diluted $100$ times, then it will become :

• A. Neutral
• B. Basic
• C. Unakected
• D. More acidic

Answer 1

The correct option is A Neutral

$pH=5$
$[H_{2}O{]}^{+}={10}^{-pH};Let{V}_1=x,V_2=100x,M_2=?$
According to dilution law,
$M_1{V}_1=M_2{V}_2$
${10}^{-5}x=M_{2}100x$
$\frac{{10}^{-5}x}{100x}=M_2$ or $M_2={10}^{-7}$
$\left[H_3{O}^{+}\right]={10}^{-7}+{10}^{-7}$ M from water
$ -2 \times 10^{-7}\, M$
$pH=-log\left[H_3{O}^{+}\right]=-log(2\times {10}^{-7})=6.69$
Hence, solution becomes almost neutral.