In: Chemistry
Determine the mass of sucrose (C12H22O11) needed to lower the freezing point of 100.0 g of water by 3.00 oC. (Kf = 1.86 oC kg/mol).
Depression in the freezing point =
, where Kf = 1.86 oC. kg/mol and m= molality of the solution
Given
3 = 1.86 (m)
molality = 1.61 m
But
Molality = moles of the solute/ weight of the solvent(kg)
weight of the solvent = 100 g = 0.100 L
1.61 = moles /0.100
Moles of the solute, sucrose = 0.161 moles
Molar mass of sucrose (C12H22O11) = 342.3 g/mol
Mass of the sucrose =
Mass of sucrose needed = 55.2 g