2.2 Expression of Concentration of Solutions
The composition of a solution can be expressed qualitatively or quantitatively:
- Qualitative description:
- Dilute solution → Contains a small amount of solute.
- Concentrated solution → Contains a large amount of solute.
- Quantitative description:
- Provides precise numerical values to describe the solution’s concentration.
Methods to Express Concentration Quantitatively
1. Mass Percentage (w/w%)
- Definition: The mass percentage of a component in a solution is the mass of the component per 100 g of the solution.
- Formula:
Mass%= (mass of the component in the solution/Total mass of the solution)×100
- A 10% glucose solution means 10 g of glucose is dissolved in 90 g of water, making the total mass 100 g.
- Application: Used in industrial chemical formulations (e.g., commercial bleaching solution contains 3.62% sodium hypochlorite in water).
2. Volume Percentage (v/v%)
- Definition: The volume percentage of a component is the volume of the component per 100 mL of the solution.
- Formula:
Volume % of a component= (Volume of the component/Total volume of the solution)×100
- A 40% alcohol solution means 40 mL of alcohol is mixed with 60 mL of water, making the total volume 100 mL.
- Application: Used in alcoholic beverages, perfumes, and liquid medicinal formulations.
Would you like me to continue with other concentration methods like molality, molarity, mole fraction, or ppm?