Question

Calculate the mass of compound to be dissolved in 75g of benzene to lower its freezing point by 0.48 K. (Given: K_f = 0.512 K kg mol^-1 and molar mass = 256g mol^-1)

Answer 1

Given: K_f = 0.512 K kg mol^-1, M₂ = 256g mol^-1, ΔT_f = 0.48 K, W1 = 75g

`DeltaT_f=(K_fxxW_2)/(W_1xxM_2)`

`W_2 = (DeltaT_fxxW_1xxM_2)/K_f`

`W_2 = (0.48xx75xx256)/512g`

`=9216/512g=18g`

Mass of compound, W₂ = 18g