# How do you calculate the number of moles from concentration?

Jan 8, 2014

You multiply the concentration (in moles per litre) by the volume in litres.

The number of moles of a substance in one litre of solution is called its molarity. The official symbol for molarity is “c” (concentration), but most people use the symbol “M”.

M = $\frac{n}{V}$,

where n is the number of moles and V is the volume in litres.

We can rearrange this equation to get the number of moles:

n = M × V

Example:
How many moles of NaCl are contained in 0.300 L of 0.400 mol/L NaCl solution?

Solution:
n = 0.300 L soln × (0.400 mol NaCl/1 L soln) = 0.120 mol NaCl