Question

Phosphoric acid is commonly supplied as an 85% solution. What mass of this solution would be required to prepare 600.0 mL of a 2.80 M phosphoric acid solution?

Answer 1

You would need to use 194 g of the 85 % H₃PO₄.

You must make the following conversions:

Volume of dilute acid → moles of H₃PO₄ → mass of H₃PO₄ → mass of 85 % H₃PO₄

0.6000 L dil. acid × `("2.80 mol H"_3"PO"_4)/"1 L dil. acid" × ("98.00 g H"_3"PO"_4)/("1 mol H"_3"PO"_4)` ×

`("100 g 85 % H"_3"PO"_4)/("85 g H"_3"PO"_4) = "194 g of 85 % H"_3"PO"_4`