How many grams of methanol are needed to raise the boiling point of 250 mL of water by 2.7C. The boiling point elevation constant for water = 0.512 C/m. Assume water to have a density of 1g/mL)

Answer 1

delta T = Kb*molality
2.7 = 0.512*m
solve for m

molality = moles/kg solvent
You have molality, kg = 0.250, solve for moles.

moles = g/molar mass. solve for g.

I don't think this is a good problem because the depression of freezing point and elevation of boiling point are based on NON-VOLATILE solutes and methanol is hardly non-volatile.