Question

When 1.150 grams of an unknown nonelectrolyte dissolves in 10.0 grams of water, the solution freezes at -2.16°C. What is the molecular weight of the unknown compound? Kf for water = 1.86°C/m.

-2.16 x m/-1.86 = 1.16

1.16/ .010 kg of water= 116

1.150/116= 9.91 g/mol is the answer I got.
However, the answer is 99.1 per mole. So where would I be going off by a decimal place.

Answer 1

delta T = Kf*molality
Substitute and solve for molality.

m = mols/kg solvent
Substitute and solve for mols.

mols = grams/molar mass
You know mols and grams, solve for molar mass.

Answer 2

Show me ir solution