The mass of NaOH required to make a 500 mL solution of 0.5 molarity is

10 g

The correct answer is Option (4) → 10 g

Molarity $M = \frac{\text{moles}}{\text{volume (in L)}}$

Given:

• $M = 0.5\ \text{M}$
• Volume = $500\ \text{mL} = 0.5\ \text{L}$

$\text{Moles of NaOH} = 0.5 \times 0.5 = 0.25\ \text{mol}$

Molar mass of NaOH = $40\ \text{g mol}^{-1}$

$\text{Mass} = 0.25 \times 40 = 10\ \text{g}$