A worked example
2 moles of solute dissolved in 0.5 liters of solution gives a molarity of exactly 4M.
Frequently asked questions
What does 'M' mean as a unit?
M stands for molar — shorthand for moles per liter, the standard unit for molarity. A '1M' solution contains exactly 1 mole of solute per liter of total solution.
Why does diluting a solution lower its concentration?
The total amount of solute (moles) stays exactly the same when you dilute — only the volume increases by adding solvent, so the same amount of solute is now spread through more liquid, lowering the concentration proportionally.