What is Molarity?
Molarity (M) is the concentration of a solution — the number of moles of solute dissolved in one litre of solution. It's the most common way chemists measure how strong a solution is.
Molarity is moles of solute per litre of solution: M = n/V. A 1 M solution contains 1 mole of dissolved substance in 1 litre total volume.
Try it: interactive calculator
Step-by-step worked examples
How many moles of NaCl are in 2 L of a 0.5 M solution?
M = n/V 0.5 = n/2 n = 0.5 × 2 = 1 mole NaCl
A solution contains 3 moles of glucose in 1.5 L. What is its molarity?
M = n/V M = 3/1.5 M = 2 mol/L
To make 500 mL of 0.2 M KCl, how many moles are needed?
500 mL = 0.5 L M = n/V 0.2 = n/0.5 n = 0.2 × 0.5 = 0.1 mol KCl
Flashcards
Quick quiz
Q1.3 moles in 2 L. Molarity?
Q2.Unit of molarity?
Q3.0.1 M, 500 mL solution. Moles?
Q4.Which affects molarity?
The full card deck, worked steps and AI-tutor support for “What is Molarity?” are in Notek — study by hand before your exam.
Common mistakes
Using volume of solvent only instead of total solution volume. — Correct: V is the TOTAL volume of solution (solute + solvent), not solvent alone.
Confusing molarity M with molality m. — Correct: Molarity is mol/L of solution; molality is mol/kg of solvent.
Forgetting to convert mL to L. — Correct: Always convert volume to litres before calculating molarity.
Thinking more concentrated = higher volume. — Correct: Concentration (M) depends on moles and volume; same moles in less volume = higher M.
FAQ
What is molarity formula?
M = n/V, where n is moles of solute and V is litres of solution.
Why is molarity useful?
It directly tells chemists how many particles per litre — essential for reactions and stoichiometry.
Difference between molarity and molality?
Molarity = mol/L of solution (temperature-dependent); molality = mol/kg of solvent (fixed).
Can molarity change with temperature?
Yes. As temperature increases, volume increases → molarity decreases.