Concentration and Molarity
Molarity is moles of solute per litre of solution.
About this topic
Concentration measures how much solute is dissolved in a given amount of solution. Molarity (M) is moles of solute per litre of solution: M = n / V. A 1.0 M NaCl solution contains 1.0 mol (58.44 g) of salt in every litre of solution.
Note that the volume is that of the final solution, not the solvent alone. To make a solution, weigh the solute, dissolve it in less than the full volume of water in a volumetric flask, then fill up to the mark and mix. Rearranged, n = M x V and V = n / M. Molarity lets chemists treat the amount of a solution like a count of particles, which is convenient for reactions in water. Dilute and concentrated are qualitative terms that molarity makes exact.
Worked example: how many grams of NaOH (40.0 g/mol) are needed for 250 mL of 0.500 M solution? Moles = 0.500 x 0.250 = 0.125 mol; mass = 0.125 x 40.0 = 5.00 g. Concentration matters in medicine, where saline for drips is about 0.15 M, and in pools, cleaning agents and car batteries.
A frequent mistake is to use millilitres without converting to litres. Another is thinking that 1 litre of water plus solute gives 1 litre of solution; the volumes are not exactly additive.
Key ideas
- M = n / V
- Dilution: M₁V₁ = M₂V₂
- Units mol/L
Quick check
Use cases: where Concentration and Molarity helps
- Homework: review the key idea behind Concentration and Molarity before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Concentration and Molarity without notes.
- Visual learning: play with the interactive lab to see how Concentration and Molarity changes when you adjust its inputs.
- Teaching a friend: explain Concentration and Molarity 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 Concentration and Molarity?
Molarity is moles of solute per litre of solution.
What will I learn in Concentration and Molarity?
M = n / V. Dilution: M₁V₁ = M₂V₂. Units mol/L.
Is Concentration and Molarity 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 Concentration and Molarity 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 Concentration and Molarity?
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?
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