Question

A 20.0 % by mass solution of phosphoric acid (H 3PO 4) in water has a density of 1.114 g/mL at 20°C. What is the molarity of this solution?

Answer 1

2.28 M

Step-by-step explanation:

Step 1: Given data

Percent by mass (%m/m): 20.0 %

Density (ρ): 1.114 g/mL

Step 2: Calculate the percent by volume (%m/v)

We will use the following expression.

`\% m/v = \% m/m * \rho = 20.0 \% * 1.114g/mL = 22.3 g \% mL`

Step 3: Calculate the moles of solute in 100 mL of solution

The molar mass of phosphoric acid is 97.99 g/mol. The moles corresponding to 22.3 g are:

`22.3g * (1mol)/(97.99g) = 0.228mol`

Step 4: Calculate the molarity of the solution

0.228 moles of solute are in 100 mL (0.100 L) of solution. The molarity of the solution is:

`M = (0.228mol)/(0.100L) =2.28 M`