Question

An acid solution has a $pH=6$. It is diluted 100 times, the $pH$ of the resultant solution would be

• A. $5.95$
• B. $6.95$
• C. $7$
• D. $8$

Answer 1

Answer: (B)

For original undiluted solution,
$pH=6$
$\left[H_3{O}^{+}\right]=10^{-pH}=10^{-6}M$
The solution is diluted 100 times.
For the final diluted solution
$\left[H_3{O}^{+}\right]=\frac{10^{-6}M}{100}=10^{-8}M$
But there will be $\left[H_3{O}^{+}\right]$due to autoionisation of water.
In any way, since solution is acidic, $\left[H_3{O}^{+}\right]>10^{-7}M$ and $pH<7$
Hence, the $pH$ of solution becomes $6.95$.