Molarity (M)
Moles of solute dissolved per litre of solution; temperature dependent.
What is Molarity (M)?
The number of moles of solute dissolved in one litre of solution.
Key formula / rule: Molarity
Key points
- Define molarity.
- Calculate molarity given moles of solute and volume of solution.
- Calculate molarity given mass of solute, molar mass, and volume of solution.
- Understand the temperature dependence of molarity.
Common exam trap
Confusing molarity with molality (temperature-dependent vs. independent).
Definitions
- Term
Molarity
- Meaning
The number of moles of solute dissolved in one litre of solution.
- Term
Solute
- Meaning
The substance that is dissolved in a solvent to form a solution.
- Term
Solution
- Meaning
A homogeneous mixture of two or more substances.
Learning objectives
Define molarity.
Calculate molarity given moles of solute and volume of solution.
Calculate molarity given mass of solute, molar mass, and volume of solution.
Understand the temperature dependence of molarity.
Differentiate molarity from molality.
Formulae
- Name
Molarity
- Note
Where n is the number of moles of solute and V(L) is the volume of the solution in litres.
- Expression
M = n / V(L)
- Name
Moles of solute
- Note
Used to calculate moles when mass is given.
- Expression
n = mass of solute / molar mass of solute
- Name
Volume conversion
- Note
To convert volume from millilitres to litres.
- Expression
V(L) = V(mL) / 1000
Prerequisites
Concept of moles.
Atomic and molecular masses.
Units of volume (litres, millilitres).
Basic arithmetic and algebraic manipulation.
Common mistakes
Confusing molarity with molality (temperature-dependent vs. independent).
Using volume of solvent instead of volume of solution in calculations.
Not converting given volume units (e.g., mL) to litres.
Incorrectly calculating moles of solute from mass.
Keywords
Molarity
Concentration
Solution
Solute
Moles
Volume
Temperature Dependent
Molar
Molar Mass
Practice preview
Which of the following concentration terms is temperature dependent?…
easy
If 200 mL of a 0.5 M H₂SO₄ solution is diluted to 1 L, what will be the new molarity?…
medium
A solution is prepared by dissolving 18 g of glucose (molar mass = 180 g/mol) in 100 g of water. The density of the solution is 1.1 g/mL. What is the molarity of the solution?…
hard