Question

How do you calculate the number of moles from concentration?

Answer 1

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 = `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