Dilution concepts
By the end of this lesson
- Use compatible units in C1V1 = C2V2
- Distinguish stock draw from final volume
- Check chemical suitability before diluting
Examples use a decimal point; a comma groups thousands.
See it
Dilution reduces concentration by adding an appropriate diluent while conserving the amount of solute. The familiar relationship C1V1 = C2V2 is useful when the concentration definitions and units are compatible.
Understand it
Use compatible units in C1V1 = C2V2
C1 and C2 must describe the same substance and compatible concentration units.
V2 is the complete final solution volume, including the stock contribution.
Distinguish stock draw from final volume
V1 is the amount of stock required; V2 is the final diluted volume.
Conservation-based dilution calculations require the same solute and compatible concentration and volume definitions.
Check chemical suitability before diluting
A dilution is useful only if the new measurement becomes practical and the chemistry remains appropriate.
Rearrange to V1 = C2V2/C1: 2 mg/mL × 5 mL ÷ 10 mg/mL = 1 mL.
Worked example
For an arithmetic-only example, dilute a compatible 10 mg/mL stock to 2 mg/mL with a final volume of 5 mL. V1 = C2 × V2 / C1 = 2 × 5 / 10 = 1 mL of stock. Bring it to 5 mL final volume using the appropriate diluent; do not add 5 mL on top. This is not a plant-treatment recipe.
Explain your decision before opening the worked reasoning below.
Show the worked reasoning
A final-volume instruction means the stock is part of that total; adding the full target volume again would overshoot it.
Dilution should solve a real measurement problem without violating solvent, stability or protocol constraints.
Do not create a dilution merely to make the arithmetic convenient without checking chemical suitability.
Try it
How much stock is required in the worked example?
Use the worked example above to explain your answer in your own words before taking the quiz.
Lesson quiz
Assessment version: 2026-10-15-v2. Previous reading-completion markers are retained. This revised quiz has its own result.
Apply it
Use the worked example to write a short decision record: what did you observe, which rule did you apply, and what would you check before acting?
Completion marks reading progress, not a quiz pass or professional certification.