Question

If the $pH$ of an aqueous solution is $4.7$, then its $H ^{+}$concentration will be

• A. $ 3\times 10^{-6}$
• B. $ 3\times 10^{-5}$
• C. $ 2\times 10^{-5}$
• D. $ 5\times 10^{-5} $

Answer 1

Answer: (C)

$p H =-\log \left[ H ^{+}\right]$
Here, $pH =4.7 $
$ \therefore 4.7 =-\log \left[ H ^{+}\right] $
$4.7 =\log \left[ H ^{+}\right]^{-1} $
Antilog $4.700 =\left[ H ^{+}\right]^{-1} $
$ 50120.0 =\frac{1}{\left[ H ^{+}\right]} $
$\left[ H ^{+}\right] =\frac{1}{50120} $
$\left[ H ^{+}\right] =0.00002 $
$\left[ H ^{+}\right] =2 \times 10^{-5} $