Question

The $pH$ of $HCl$ is $1$. The amount of $NaOH$ to be added to $100ml$ of such a $HCl$ solution to get $pH$ of $7$ is

• A. $4g$
• B. $0.4g$
• C. $4mg$
• D. $0.4mg$

Answer 1

Answer: (A)

$4g$

$pH=4$

$\Rightarrow \left[H^{+}\right]={10}^{-1}$

$NaOH+HCl\to NaCl+H_{2}O$

Since 1 mole $HCl$ is neutralized by 1 mole $NaOH$

$\Rightarrow$ 0.1 mole $HCl$ is neutralized by 0.1 mole $NaOH$

Mass of $NaOH=0.1\times 40=4g$