Molarity
M = n / V = mol / L
Molarity is the most common concentration unit in chemistry. It expresses concentration as moles of solute per liter of solution and is essential for solution stoichiometry.
Variables
Concentration in mol/L (also written as M)
Amount of dissolved substance in moles
Total volume of solution in liters
Example Calculation
Scenario
What is the molarity of a solution made by dissolving 4.00 g of NaOH in enough water to make 250 mL of solution?
Given Data
Calculation
n = 4.00 g / 40.00 g/mol = 0.100 mol; M = 0.100 mol / 0.250 L
Result
M = 0.400 M NaOH
Interpretation
The solution contains 0.400 moles of sodium hydroxide per liter. This is a moderately concentrated basic solution.
When to Use This Formula
- ✓Preparing solutions of specific concentration
- ✓Solution stoichiometry calculations
- ✓Titration calculations
- ✓Dilution problems (M1V1 = M2V2)
Common Mistakes
- ✗Using volume of solvent instead of solution
- ✗Forgetting to convert mL to L
- ✗Confusing molarity with molality
- ✗Not dissolving completely before measuring final volume
Calculate This Formula Instantly
Snap a photo of any problem and get step-by-step solutions.
Download ChemistryIQFAQs
Common questions about this formula
M1V1 = M2V2 relates initial and final concentrations and volumes during dilution. Since moles of solute stay constant, the product of concentration times volume is constant.
Molarity (M) is moles per liter of solution. Molality (m) is moles per kilogram of solvent. Molality is temperature-independent and used for colligative properties; molarity is more convenient for volumetric work.