2.2 Expression of Concentration of Solutions 3

 

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?