Question

A solution of $NaOH$ contains 0.04g of $NaOH$ per litre. Its $pH$ is:

• A. $10$
• B. $9$
• C. $11$
• D. $12$

Answer 1

Answer: (C)

$11$

Given $0.04g$ of $NaOH$ is in $1000ml$

Molarity= $\frac{0.04}{40}\times \frac{1000}{1000}=0.001={10}^{-3}$

$\Rightarrow pOH$ of $NaOH=-\log \left[O{H}^{-}\right]=-\log \left[{10}^{-3}\right]=3$

$\Rightarrow pH+pOH=14$

$\Rightarrow pH+pOH=14$

$\Rightarrow pH=14-3=11$

$\therefore pH$ of $NaOH$ is $11$ .