Question

If you add water to a 15.00 mL solution of 3.22 M CaCl2 (MM=110.98 g/mol) in order to create a solution that is 15.00% CaCl2 by mass, what is the final mass of the new solution. The density of water is exactly 1.00 g/mL. Assume that the density of the CaCl2 solution is also exactly 1.00 g/mL.

Answer 1

The mass of the new solution is 35.7 g.  

Step 1. Calculate the moles of CaCl₂ in the first solution.  

[$\text{Moles of CaCl}_{2} = \text{0.015 00 L solution} \times \frac{\text{3.22 mol CaCl}_{2}}{\text{1 L solution }} = \text{0.048 30 mol CaCl}_{2}$  

Step 2. Calculate the mass of CaCl₂.  

$\text{Mass of CaCl}_{2} = \text{0.048 30 mol CaCl}_{2} \times \frac{\text{110.98 g CaCl}_{2} }{\text{1 mol CaCl}_{2} } = \text{5.360 g CaCl}_{2}$  

Step 3. Calculate the mass of the new solution.

$\text{Mass of solution }= \text{5.360 g CaCl}_{2} \times \frac{\text{100 g solution }}{\text{15.00 g CaCl}_{2} } = \textbf{35.7 g solution}$