Question

The density of a solution containing $40\%$ by mass of $HCl$ is 1.2 g/mL. Calculate the molarity of the solution.

• A. 11.15 M
• B. 12.15 M
• C. 13.15 M
• D. 14.15 M

Answer 1

Answer: (C)

13.15 M

Molarity = $\frac{moles}{volume\left(inmL\right)}\times$1000

40% by mass of $HCl$ means 100g solution contains 40g HCl.

Number of moles of $HCl=\frac{weight}{molecularmassofHCl}=\frac{40}{36.5}=1.0958$ moles

Density$=\frac{mass}{volume}=$1.2 g/mL

Volume$=\frac{100}{1.2}=83.33mL$

Therefore, Molarity = $\frac{1.0958}{83.33}\times 1000$ = 13.15 M