Chem stuff good stuff

Question

You make a solution by mixing 40.3 grams of MgCl2 with 750.0 grams of water. What is the molality of the solution?

Answer 1

Again, as in the previous question, m (molality) is defined as moles of solute/kg of solvent.

We are given g of solute so we must convert that to moles of solute.

We are given g of solvent so we must convert that to kg of solvent.

moles of solute = 40.3 g MgCl₂ x 1 mole/95.2 g = 0.423 moles MgCl₂

kg of solvent = 750.0 g H₂O x 1 kg/1000 g = 0.750 kg H₂O

molality (m) = 0.423 moles/0.750 kg = 0.564 m (to 3 signifiant figures)