Question

An unknown nonvolatile solute weighing 2.64 g is dissolved in 36.5 g of carbon

tetrachloride, CCl4. The addition of the solute causes an elevation of 1.25o

C in the

boiling point. What is the molar mass of the solute?

Answer 1

∆T_b = K_bm

K_b for CCl₄ = 4.88 °C/mol/Kg

∆T_b =1.25 °C

m = n/W where W = 0.0365Kg (mass of solvent)

so ,

1.25 = 4.88 × (n/0.0365)

On solving n = 0.0093 moles

molar mass of solute = 2.64/0.0093 = 283.8 gram