The boiling point of water at 756 mm Hg is 99.85 degree C. What mass percent of surcrose (C12H22O11) should be present to raise the boiling point to 100.00 degree C at this pressure?

Answer 1

delta T = Kb*molality.
Solve for molality.

molality = moles/kg solvent.
I would use 100 g water (0.1 kg) and solve for moles.

moles = grams/molar mass.
Solve for grams.

You now have grams in 0.1 kg solvent. You convert that to mass percent.