Question

The normal boiling point of ethyl acetate is 77.06°C. A solution of 50 g of non-volatile solute in 150 g ethyl acetate boils at 82.60°C. Calculate the molar mass of solute. [K_b = 2.77°C kg mol⁻¹]

Answer 1

Given: `T_b^0` = 77.06°C, T_b = 82.60°C, W₂ = 50 g, W₁ = 150 g, K_b = 2.77°C kg mol⁻¹

Formula: `M_2 = (1000  K_b  W_2)/(W_1  ΔT_b)`

`ΔT_b = T_b - T_b^0`

= 82.60 − 77.06

= 5.54

∴ `M_2 = (1000 xx 2.77 xx 50)/(150 xx 5.54)`

= 166.6 g mol⁻¹