# How can I find percent concentration from density?

##### 1 Answer

This is usually part of a problem that asks you to convert from one set of concentration units to another.

For example, you need the density to convert from molarity to percent concentration.

Here's a typical problem.

What is the percent concentration of a 13.0 mol/L solution of phosphoric acid that has a density of 1.464 g/mL?

**1,** Assume some fixed volume of the solution.

For convenience, let's assume a volume of 1 L.

**2.** Calculate the mass of H₃PO₄.

1 L soln ×

**3.** Use the density to calculate the mass of the solution.

1000 mL soln ×

**4.** Calculate the percent concentration

% by mass =

The solution is 87.0 % H₃PO₄ by mass.