# Question #9d93c

Apr 29, 2017

You need 56 g of water and 44 g of the 85 % acid.

#### Explanation:

In 100 g of 37 % acid, you have 37 g ${\text{H"_3"PO}}_{4}$.

$\text{Mass of 85 % acid needed" = 37 color(red)(cancel(color(black)("g H"_3"PO"_4))) × "100 g 85 % acid"/(85 color(red)(cancel(color(black)("g H"_3"PO"_4)))) = "44 g 85 % acid}$

∴ Add 56 g of water to 44 g of 85 % acid to get 100 g of 37 % acid.