Question

calculate the necessary amounts of solutes and solvent to make a 4l bottle of antifreeze that will have a 35 degree change in the freezing point of water. soultes are: Al2(SO4), KBr) and Mg(NO3)2.

Answer 1

Are you assuming 4L H2O has a mass of 4,000 g (a density of 1.0 g/mL)? AND that the addition of the Al2(SO4)3, KBr, and Mg(NO3)2 will not change the volume? You can't solve this problem without knowing the density of each of the solutions unless those assumptions are made.
delta T = i*Kf*molality
Solve for molality. See i at bottom of this response.

molality = moles/kg solvent
Solve for moles.

grams = moles x molar mass
Solve for grams.
i = 5 for Al2(SO4)3
i = 2 for KBr
i = 3 for Mg(NO3)2

Answer 2

thanks