# How can I calculate the moles of ions in solutions?

Dec 17, 2014

Concentration is usually expressed as moles per cubic decimetre or moles per litre.

$c = \frac{n}{v}$

So $n = c v$

So to find the number of moles we multiply concentration by volume.

E.g how many moles of NaCl in $25 c {m}^{3}$ of a solution of concentration $2.0 m o l . {\mathrm{dm}}^{- 3}$ ?

$n = c v = \frac{25}{1000} \times 2 = 0.05 m o l$

Note I divide by 1000 to convert $c {m}^{3}$ to ${\mathrm{dm}}^{3}$.