Question

The boiling point to a solution containing 50 gm of a non-volatile solute in 1 kg of solvent is 0.5° higher than that of pure solvent. Determine the molecular mass of the solute (give molecular mass of solvent) = 78 g mol^–1 and kb for solvent = 2.53 km^–1)

Options

• 20 g mol^–1 

• 215 g mol^–1 

• 125 g mol^–1 

• 253 g mol^–1 

Answer 1

253 g mol^–1 

Explanation:

MB = `(kb xx WB)/(ΔTb xx WA)`

= `((2.253  kg  mol^-1) xx (50  g))/((0.5  k) xx 1  kg)`

= 253 g mol^–1.