How do you calculate the number of moles from molarity and volume?

Jan 8, 2014

You multiply the molarity by the volume in litres.

Explanation:

Molarity is the number of moles of a substance in one litre of solution. The official symbol for molarity is “c” (concentration), but many people use the old 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 $\text{NaCl}$ are contained in 0.300 L of 0.400 mol/L $\text{NaCl}$ solution?

Solution:

n = 0.300 color(red)(cancel(color(black)("L soln"))) × "0.400 mol NaCl"/(1 color(red)(cancel(color(black)("L soln")))) = "0.120 mol NaCl"