The amount of urea required to make a 500 mL solution of 20% (w/w) concentration is

100 g

The correct answer is Option (3) → 100 g

A 20% (w/w) solution means 20 g of solute in 100 g of solution.

We are asked for 500 mL of solution. Assuming the density ≈ 1 g/mL, 500 mL ≈ 500 g solution.

$\text{Mass of urea} = \frac{20}{100} \times 500 = 100\text{ g}$