To determine the masses of each component, we need to know the concentration first in terms of molality which is mol per mass of solution. Assuming the density of the solution is equal to that of water we would find:
molality = 0.160 mol KBr / L ( 1 L / 1 kg solution ) = 0.160 mol KBr / kg solution
mass KBr = 0.160 mol KBr / kg solution (.0750 kg solution ) ( 119 g KBr / mol KBr ) = 1.428 g KBr
mass solvent = 75 - 1.428 = 73.572 g water
