What would be the molality of 20% (mass/mass) aqueous solution of KI?

Correct option is C. 1.51

Let's assume we have 100 g of the solution.
This means we have 20 g of KI and 80 g of water.

The molar mass of KI is approximately 39 (K) + 127 (I) = 166 g/mol.

Number of moles of KI = (mass of KI) / (molar mass of KI) = 20 g / 166 g/mol ≈ 0.1205 mol

Molality is defined as the number of moles of solute per kilogram of solvent.

Molality = (moles of KI) / (mass of water in kg) = 0.1205 mol / (80 g * (1 kg / 1000 g)) = 0.1205 mol / 0.08 kg ≈ 1.506 mol/kg

Rounding to two decimal places, the molality is approximately 1.51 mol/kg. Therefore, the correct option is C.