Concentrated phosphoric acid is sold as a solution of 85% phosphoric acid and 15% water by mass. Given that its molarity is 15 M, calculate the density of concentrated phosphoric acid.

Respuesta :

Answer: The density of phosphoric acid is 1.98 g/mL

Explanation:

We are given:

85% phosphoric acid and 15 % water

This means that 85 grams of phosphoric acid and 15 grams of water are present in 100 grams of solution

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

[tex]\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}[/tex]       ......(1)

Density of water = 1 g/mL

Mass of water = 15 g

Putting values in equation 1, we get:

[tex]1g/mL=\frac{15g}{\text{Volume of water}}\\\\\text{Volume of water}=\frac{15g}{1g/mL}=15mL[/tex]

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

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

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:

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

Volume of phosphoric acid = Volume of solution - Volume of water

Volume of phosphoric acid = [57.82 - 15] mL = 42.82 mL

  • Now, calculating the density of phosphoric acid by using equation 1:

Mass of phosphoric acid = 85 g

Volume of phosphoric acid = 42.82 mL

Putting values in equation 1, we get:

[tex]\text{Density of phosphoric acid}=\frac{85g}{42.82mL}\\\\\text{Density of phosphoric acid}=1.98g/mL[/tex]

Hence, the density of phosphoric acid is 1.98 g/mL