Dilutions
Adding solvent lowers concentration without changing moles.
About this topic
Dilution reduces concentration by adding solvent. The moles of solute stay constant, so M1V1 = M2V2. To prepare 500 mL of 0.10 M HCl from 2.0 M stock, V1 = (0.10 × 500) / 2.0 = 25 mL; add that to water and make up to 500 mL.
The equation works because moles equal molarity times volume before and after, and diluting only changes the volume. Units for V can be any, as long as both are the same. Safety rule for acids: always add acid to water, never water to acid, since the heat released may cause boiling and splashing. Use a volumetric pipette for the stock and a volumetric flask for the final volume, and mix well. For serial dilutions, you dilute step by step, for example by a factor of 10 each time.
Example: orange squash is concentrated; adding water makes it weaker but the amount of flavouring is the same. Hospitals dilute drugs to safe doses, and labs make standards for calibration, while swimming pool managers dilute chemicals.
Misconceptions: the final volume is the water you add; in fact it is the total volume. Also, M1V1 = M2V2 works only for dilution, not for mixing two solutions of different solutes or for reactions.
Key ideas
- M₁V₁ = M₂V₂
- Moles stay the same
- Always add acid to water
Quick check
Use cases: where Dilutions helps
- Homework: review the key idea behind Dilutions before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Dilutions without notes.
- Visual learning: play with the interactive lab to see how Dilutions changes when you adjust its inputs.
- Teaching a friend: explain Dilutions in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Dilutions?
Adding solvent lowers concentration without changing moles.
What will I learn in Dilutions?
M₁V₁ = M₂V₂. Moles stay the same. Always add acid to water.
Is Dilutions part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Dilutions lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Dilutions?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.