posted by paul .
what are the normal freezing points and boiling points of the following solutions: a. 21.1g NaCl in 135mL of water b. 15.4g urea in 66.7 mL water?
moles NaCl = grams/molar mass = 21.1g/58.44 = ??
molality = moles/kg solvent = ??moles/0.135 g H2O = xx
Then delta T = i*Kf*m
i = 2; Kf = 1.86; m = xx
This will give you delta T and from that and knowing H2O usually freezes at 0C, calculate freezing point of the solution.
part b is done the same way; however, i = 1.