Understanding Concentration

1. What Concentration Means
Concentration refers to the amount of a substance (solute) present in a given volume of solution. It tells you how “strong” or “weak” a solution is. For example, a highly concentrated solution contains a large amount of solute in a small volume, while a dilute solution contains a smaller amount of solute in the same volume.

2. Common Units of Concentration
Concentration can be expressed in different units depending on the context:

• g/L (grams per litre):
  Amount of solute in grams dissolved in one litre of solution.
  Example: 5 g/L means 5 grams of solute in 1 litre.

• mg/mL (milligrams per millilitre):
  Common in medical and laboratory settings.
  Example: 2 mg/mL means 2 milligrams in 1 mL.

• mol/L (molarity, M):
  Number of moles of solute per litre of solution.
  Example: 1 mol/L means 1 mole of substance in 1 litre.

3. Relationship Between Concentration and Dilution
Dilution reduces the concentration of a solution by adding more solvent (usually water). The amount of solute remains the same, but the total volume increases.

This relationship is expressed as:
C₁V₁ = C₂V₂

Where:

• C₁ = initial concentration

• V₁ = initial volume

• C₂ = final concentration

• V₂ = final volume

Key Idea:

• As volume increases → concentration decreases

• As volume decreases → concentration increases

Example:
If you dilute 10 mL of a solution to 100 mL, the concentration becomes 10 times less (a 1:10 dilution).