Start a short session
Check your answer after each question. Use a calculator where needed.
Glucose standards · practical preparation
Dilutions and solution concentrations
Practise stock volumes, final concentrations and serial dilutions. Use C₁V₁ = C₂V₂ and keep track of the final volume.
Method and worked examples ↓Learn the method
How to approach these questions
- Use the same concentration unit for C₁ and C₂, and the same volume unit for V₁ and V₂.
- To find stock volume, use V₁ = C₂V₂/C₁.
- If volumes are assumed additive, solvent volume = final volume − stock volume.
- For serial dilutions, multiply the dilution factors. One part stock plus nine parts solvent gives ten parts in total: a tenfold dilution.
Worked examples
Prepare 20 cm³ of a 2 g dm⁻³ solution from a 10 g dm⁻³ stock. How much stock and solvent are needed?
V₁ = 2 × 20 ÷ 10 = 4 cm³ stock. Add solvent to a final volume of 20 cm³; under the additive-volume assumption this is 16 cm³ solvent.
A 16 g dm⁻³ stock undergoes two fourfold dilutions. Find the final concentration.
Each step leaves one quarter of the previous concentration. 16 ÷ 4² = 1 g dm⁻³.
Keep practising
Topic map and study list · Practical data guides · Active recall decks
Course resources
AQA A-level Biology · OCR A A-level Biology · Textbook answers
Skill coverage follows the common A-level science subject content. Check your board’s current requirements: AQA 7402 and OCR A H420.