1. Use elevation in boiling point formula

For a non-volatile solute, $\Delta T_b = K_b m$ where $m$ is the molality.

2. Find the elevation in boiling point

Given:

• Boiling point of pure water $= 373\,\text{K}$
• Boiling point of solution $= 373.52\,\text{K}$

So, $\Delta T_b = 373.52 - 373 = 0.52\,\text{K}$

3. Calculate molality

$m = \frac{\Delta T_b}{K_b} = \frac{0.52}{0.52} = 1\,\text{mol kg}^{-1}$

4. Use definition of molality

Molality is: $m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}}$

Mass of water $= 20\,\text{g} = 0.020\,\text{kg}$

Thus, $1 = \frac{n}{0.020}$ $n = 0.020\,\text{mol}$

5. Find molar mass of solute

Given mass of solute $= 2\,\text{g}$

$M = \frac{\text{mass}}{\text{moles}} = \frac{2}{0.020} = 100\,\text{g mol}^{-1}$

6. Final answer

The molecular mass of the solute is $\boxed{100\,\text{g mol}^{-1}}$

Nearest integer = $100$.