VerifiedHint: Start this question by defining concentration and then its units. After this, write different methods for calculation of concentration of a solution and interconnect them.
Complete answer:
The Concentration of a Solution is defined as the relative amount of solute present in a solution.
Methods of Expressing Concentration of Solutions are as given below –
1. Percentage by weight
Symbol: (W / W %)
Definition: “It is the amount of solute present in 100 g of solution”.
Formula: $ \text{weight percent (}\dfrac{\text{W}}{\text{W}}\text{) = }\dfrac{\text{weight of solute}}{\text{weight of solution}}\text{x100 }\!\!%\!\!\text{ } $
Unit: unitless
2. Percentage by volume
Symbol: (V / V %)
Definition: “It is defined as the volume of solute present in 100 mL of solution”.
Formula: $ \text{volume percent (}\dfrac{\text{V}}{\text{V}}\text{) = }\dfrac{\text{volume of solute}}{\text{volume of solution}}\text{x100 }\!\!%\!\!\text{ } $
Unit: unitless
3. Weight by volume
Symbol: (W / V %)
Definition: “It is defined as the amount of solute present in 100 mL of solution”.
Formula: $ \text{weight/volume percent (}\dfrac{\text{W}}{\text{V}}\text{) = }\dfrac{\text{weight of solute (g)}}{\text{volume of solution (L)}}\text{x100 }\!\!%\!\!\text{ } $
Unit: g/L
4. Mole fraction
Symbol: $ \chi $
Definition: “It is the ratio of the number of moles of solute and the total number of moles of solute and solvent”.
Formula: $ {{\chi }_{\text{solute}}}=\dfrac{\text{moles of solute}}{\text{total moles of all components}} $
Unit: unitless
5. Parts per million
Symbol: ppm
Definition: “It is defined as the parts of a component per million parts ( $ \text{1}{{\text{0}}^{\text{6}}} $ ) of the solution. It is widely used when a solute is present in trace quantities”.
Formula: $ \text{PPM=}\dfrac{\text{mass of solute}}{\text{mass of solution}}\text{x1}{{\text{0}}^{\text{6}}} $
Unit: ppm
6. Molarity
Symbol: M
Definition: “Molarity of any solution is the number of moles of solute per litre of solution”.
Formula: $ \text{Molarity=}\dfrac{\text{moles of solute (mol)}}{\text{volume of solution (L)}} $
Unit: mol/L
7. Molality
Symbol: m
Definition: “Molality of any solution is represented as the number of moles of solute present per kg of solvent”.
Formula: $ \text{Molality=}\dfrac{\text{moles of solute (mol)}}{\text{weight of solvent (kg)}} $
Unit: mol/kg
8. Normality
Symbol: N
Definition: “It is defined as the gram equivalent weight per litre of solution”.
Formula: $ \text{Normality = }\dfrac{\text{mass of solute (g)}}{\text{equivalent mass x volume of solution (L)}} $
Unit: gram equivalent/ L.
Note: Concentration is basically a measure to find the amount of solute present in a solvent which together forms a solution.
