Question

Muriatic acid is an old name for hydrochloric acid. The commercial grade (impure) solution is still sold as muriatic acid. You use it in toilet bowl cleaners, for cleaning masonry, and for adjusting the pH of swimming pools. My local hardware store sells muriatic acid labelled as 31.5 % HCl. Its density is 1.16 g/mL. Assume you have 1 L of this muriatic acid (MA). Determine the molarity given this information.

Answer 1

10.0M should be the correct answer

Answer 2

Answer: The molarity of HCl in the solution is 10.01 M

Explanation:

We are given:

31.5 % HCl in muratic acid

This means that 31.5 grams of HCl is present in 100 grams of solution

To calculate the volume of solution, we use the equation:

$\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}$

Density of solution = 1.16 g/mL

Mass of solution = 100 grams

Putting values in above equation, we get:

$1.16g/mL=\frac{100g}{\text{Volume of solution}}\\\\\text{Volume of solution}=\frac{100g}{1.16g/mL}=86.21mL$

To calculate the molarity of solution, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}$

Given mass of HCl = 31.5 g

Molar mass of HCl = 36.5 g/mol

Volume of solution = 86.21 mL

Putting values in above equation, we get:

$\text{Molarity of solution}=\frac{31.5\times 1000}{36.5g/mol\times 86.21}\\\\\text{Molarity of solution}=10.01M$

Hence, the molarity of HCl in the solution is 10.01 M