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Chemistry · Grades 9–12

Concentration and dilution

Count solute amount before and after adding solvent.

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Concentration

Molar concentration c = n/V uses solution volume in liters.

Dilution

In a simple dilution without reaction or solute loss, c₁V₁ = c₂V₂.

Volume

Final solution volume is not the same as the volume of added solvent.

Units

Convert milliliters to liters for c = n/V; ratios may use matching volume units.

Worked examples

Find concentration for 0.15 mol in 0.50 L of solution.

c = 0.15/0.50 = 0.30.

0.3 mol/L

How many liters are in 250 mL?

Divide milliliters by 1000.

0.25 L

Check your understanding

  1. A 20 mL aliquot at 0.50 mol/L is diluted to 100 mL total. Find the new concentration.

  2. During dilution with no loss or reaction, what stays unchanged?

    1. The solution volume.
    2. The concentration.
    3. The amount of solute.

  3. How many moles are in 0.20 L of a 0.40 mol/L solution?

Answers and marking notes

Answers and marking notes
  1. 0.1 mol/L

    c₂ = 0.50 × 20/100 = 0.10.

  2. The amount of solute.

    Adding solvent lowers concentration but preserves solute amount.

  3. 0.08 mol

    n = cV = 0.40 × 0.20 = 0.080.

Further reading and review references

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Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.