Determine the freezing point of an aqueous solution containing 10.50 g of magnesium bromide in 200.0 g of water.

Answer 1

mols MgBr2 = grams/molar mass = ?
m solution = mols MgBr2/kg solution.
Then delta T = i*Kf*m
i for MgBr2 = 3
You know Kf and m, solve for delta T, then subtract from zero to find new freezing point.

Answer 2

-1.59 degrees Celsius