Question

Calculate the mass of ascorbic acid (molecular mass = 176 g/mol) that should be dissolved in 155 g of acetic acid to cause a depression of the freezing point by 1.15 K. Assume that ascorbic acid does not dissociate or associate in the solution. (K_f for acetic acid = 3.9 K kg/mol)

Answer 1

Mass of acetic acid (ω₁) = 155 gm

Molar mass of ascorbic acid = 176 g mol^-1

Lowering melting point, ΔT_f = 1.15 K

`Delta "T"_"f" = ("K"_"f" xx 1000 xx omega_2)/("M"_2 xx omega_1)`

`omega_2 = (1.15 xx 176 xx 155)/(3.9 xx 1000)`

`omega_2 = 8.044` gm

Hence, 8.044 g of ascorbic acid is needed to be dissolved.