Question

Molarity of 4% (w/v) solution of NaOH is

• A. 0.1
• B. 0.5
• C. 0.001
• D. 1.0

Answer 1

Answer: (D)

Correct option: (C)

Molarity is defined as the number of moles of a solute dissolved in one litre of solution.

$\text{Molarity}=\frac{\text{Number of moles of solute}}{\text{Volume of solution(mL)}}\times 1000$

Step 1: Calculating the number of moles of $NaOH$

$4$% $\left(W/V\right)$ means $4g$ of $NaOH$ is present in $100mL$ of solution.

Molecular weight of $NaOH=40g/mol$

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molecular mass}}$

$\text{Number of moles}=\frac{4g}{40g/mol}=0.1mol$

Step 2: Calculating molarity of solution

Volume of solution $=100mL$

$\text{Molarity}=\frac{0.1}{100}\times 1000=1M$