Molality
is one way of expressing concentration of a solute in a solution. It is expressed
as the mole of solute per kilogram of the solvent. To calculate for the
mass of the solute in a given solution, we need to calculate first for the number of moles of the substance by the product of the molality and the mass of the solvent. Then, we convert the number of moles into mass by using the molar mass.
moles NaCl = 0.40 m (1.5 kg water) = 0.6 mol NaCl
mass NaCl = 0.6 mol NaCl ( 58.44 g / mol ) = 35.06 g NaCl
Therefore, the correct answer would be the third option.
