# What is the percent concentration of a 300-mm solution of CaCl2?

##### 1 Answer

The solution is 3.22 % CaCl₂ by mass.

Percent by mass is the mass of the solute divided by the mass of the solution, multiplied by 100.

% by mass =

**Step 1** — Determine the mass of the water.

Assume that you have 1 kg of water.

**Step 2** — Determine the mass of CaCl₂.

A 300 mm solution contains 300 mmol of solute dissolved in 1 kg of solvent.

Mass of CaCl₂ = 1 kg water ×

**Step 3**— Determine the total mass of the solution

mass of solution = mass of CaCl₂+ mass of H₂O = (33.3 + 1000) g = 1033.3 g

**Step 4** — Determine percent composition by mass of the CaCl₂ solution.

% by mass =

The percent composition by mass of the CaCl₂ solution is 3.22 %.