Conversion of the Unit of Concentration
- The chart above shows how to convert the units of concentration from g dm-3 to mol dm-3 and vice versa.
- The molar mass of the solute is equal to the relative molecular mass of the solute.
The concentration of a Potassium chloride solution is 14.9 g dm-3. What is the molarity ( mol dm-3) of the solution? [ Relative Atomic Mass: Cl = 35.5; K = 39 ]
Relative Formula Mass of Potassium Chloride (KCl)
= 39 + 35.5 = 74.5
Molar Mass of Potassium Chloride = 74.5 g/mol
Molarity of Potassium Chloride
Molarity = Concentration Molar Mass = 14.9gd m −3 74.5gmol−1 =0.2mol/dm3
A solution of barium hydrokxide have molarity 0.1 mol dm-3. What is the concentration of the solution in g dm-3? [Relative Atomic Mass: Ba = 137; O = 16; H = 1 ]
Relative Formula Mass of barium hydrokxide, Ba(OH)2
= 137 + 2(16+1) = 171
Molar Mass of Potassium Chloride = 171 g/mol
= Molarity×Molar Mass
=0.1mol/dm3 × 171gmol−1 =17.1gmol−1