Question

Phosphoric acid is usually obtained as an 85% phosphoric acid solution. If it is 15 M, what is the density of this solution

Answer 1

Answer: The density of given solution is 1.73 g/mL

Explanation:

We are given:

85 % phosphoric acid solution

This means that 85 grams of phosphoric acid is present in 100 grams of solution

To calculate the volume of solution, we use the equation used to calculate the molarity of solution:

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

Given mass of phosphoric acid = 85 g

Molar mass of phosphoric acid = 98 g/mol

Molarity of solution = 15 M

Putting values in above equation, we get:

$15mol/L=\frac{85\times 1000}{98g/mol\times V}\\\\V=\frac{85\times 1000}{98\times 15}=57.82mL$

To calculate the density of substance, we use the equation:

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

Mass of solution = 100 g

Volume of solution = 57.82 mL

Putting values in above equation, we get:

$\text{Density of solution}=\frac{100g}{57.82mL}\\\\\text{Density of solution}=1.73g/mL$

Hence, the density of given solution is 1.73 g/mL