All courses › Chemistry 1 › Amount and concentration

Amount and concentration

Amount of substance is the number of moles, and it is mass divided by molar mass. Concentration is amount divided by the volume of the solution, not of the solvent alone. The volume must be in litres when the concentration is to be moles per litre. A solution can be made by weighing the substance, dissolving it and filling up to the mark on the flask. The volume is then what you filled up to, not the water you poured in first.

n = \frac{m}{M}

amount of substance

c = \frac{n}{V}

concentration

Symbols

$n$	amount of substance	mol
$m$	mass	g
$M$	molar mass	g/mol
$V$	volume of the solution	L
$c$	concentration	mol/L

Example

36.04 g of water has molar mass 18.02 g/mol, so $n = 36.04/18.02 = 2$ mol.

Made up to 0.50 L: $c = 2/0.50 = 4$ mol/L.

Millilitres must be divided by 1000 before they are entered as litres.

Practise amount of substance and concentration for free →

← Molar mass · Dilution →

Part of Chemistry 1: Amount of substance and concentration.