Question

1.0 g of non volatile electrolyte solute dissolve in 50 g of benzene lowered the freezing point of benzene by 0.40 K. Find the molar mass of the solute. [Kf for benzene = 5.12 K kg mol-1].

Answer 1

∆Tf= Kf x weight of solute / ( molar mass of solute x weight of solvent in kg)
o.4 = 5.12 x 1x 1000/(Mx 50)
M = 256

hope this will help you

Answer 2

Answer:

The molar mass of the solute is 256 g/mol.

Explanation:

Mass of solute = 1.0 g

Mass of solvent = 50 g = 0.050 kg

Molal freezing constant of  benzene =$K_f$ 5.12 K kg /mol

Depression in freezing point =ΔT= 0.40 K

$\Delta t=k_f\times molality$

$0.40 K =5.12 K kg/mol\times \frac{1.0 g}{M\times 0.050 kg}$

M = molar mass of solute =256 g/mol

The molar mass of the solute is 256 g/mol.