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Free chemistry tool: Calculate molarity, moles, volume & mass. Includes dilution calculator (M₁V₁=M₂V₂), solution preparation guide & molecular weight database. Perfect for students & lab professionals!
Choose your calculation method
Use the mass calculator when you know the weight of your solute
Select from common compounds for quick molar mass lookup
Dilution calculator helps prepare solutions from stock
All units are automatically converted to standard SI units
Results show multiple concentration formats for convenience
Molarity (M) is the most common unit of concentration in chemistry, expressing the number of moles of solute dissolved in one liter of solution. It's a measure of how concentrated a solution is and is essential for quantitative chemical analysis, reactions, and laboratory work.
Key Characteristics of Molarity:
| Unit | Formula | Temperature Dependent | Common Use |
|---|---|---|---|
| Molarity (M) | mol/L solution | Yes | Most lab work, reactions |
| Molality (m) | mol/kg solvent | No | Colligative properties |
| Normality (N) | equivalents/L | Yes | Acid-base titrations |
| % w/v | g/100mL | Slightly | Medical, pharmaceutical |
| ppm | mg/L | Slightly | Environmental, trace analysis |
Molarity allows precise stoichiometric calculations. Knowing the molarity helps determine exact amounts of reactants needed and products formed in solution reactions.
Standard solutions with known molarity are essential for titrations, calibrations, and quantitative analysis. Accurate molarity ensures reproducible results.
Physiological processes depend on specific molar concentrations of ions and molecules. Buffer solutions maintain pH through precise molar ratios.
Manufacturing processes require exact concentrations for quality control, product consistency, and safety compliance in chemical production.
M = n / V
Where:
Example: 0.5 moles of NaCl in 2 liters of solution
M = 0.5 / 2 = 0.25 M
M = (mass / MW) / V
Where:
Example: 117g NaCl (MW=58.5 g/mol) in 1 liter
M = (117 / 58.5) / 1 = 2 M
M₁V₁ = M₂V₂
Where:
Example: Dilute 50mL of 6M HCl to 0.5M
6 × 50 = 0.5 × V₂ → V₂ = 600mL
Add 550mL water to 50mL of 6M HCl
mass = M × V × MW
Where:
Example: Prepare 500mL of 1M NaOH (MW=40 g/mol)
mass = 1 × 0.5 × 40 = 20g NaOH
n = M × V
Where:
Example: How many moles in 250mL of 2M solution?
n = 2 × 0.25 = 0.5 moles
V = n / M
Where:
Example: What volume contains 3 moles at 1.5M?
V = 3 / 1.5 = 2 L (2000 mL)
Calculate Mass Required
Use formula: mass (g) = Molarity × Volume (L) × Molecular Weight
Example: 1M NaCl, 500mL → 1 × 0.5 × 58.5 = 29.25g
Weigh the Solute
Use analytical balance for accuracy. Tare the weighing boat/paper first.
Dissolve in Solvent
Add solute to beaker with ~70% of final volume. Stir until completely dissolved.
Transfer to Volumetric Flask
Pour solution into volumetric flask. Rinse beaker and add rinsings to flask.
Dilute to Final Volume
Add solvent until bottom of meniscus reaches calibration mark. Mix thoroughly.
Label and Store
Label with: compound name, concentration, date, preparer. Store appropriately.
Calculate Volume Needed
Use M₁V₁ = M₂V₂ to find V₁ (stock volume needed)
Example: 100mL of 0.5M from 2M → V₁ = (0.5×100)/2 = 25mL
Measure Stock Solution
Use pipette or graduated cylinder to measure V₁ accurately.
Add to Volumetric Flask
Transfer stock solution to volumetric flask of final volume (V₂).
Dilute to Mark
Add solvent to reach calibration mark. Mix well by inverting several times.
Safety Note
Always add acid to water, never water to acid!
Quick reference for frequently used chemicals in laboratory work:
Molarity (M) is the concentration of a solution expressed as moles of solute per liter of solution. Formula: M = n/V, where M is molarity (mol/L), n is moles of solute, and V is volume in liters. Example: 2 moles of NaCl in 1 liter = 2 M solution.
First calculate moles: n = mass (g) / molecular weight (g/mol). Then calculate molarity: M = n / volume (L). Example: 58.5g NaCl (MW=58.5) in 500mL: n = 58.5/58.5 = 1 mol, M = 1/0.5 = 2 M.
The dilution formula is M₁V₁ = M₂V₂, where M₁ is initial molarity, V₁ is initial volume, M₂ is final molarity, and V₂ is final volume. Example: To dilute 100mL of 2M to 0.5M: 2×100 = 0.5×V₂, V₂ = 400mL.
This molarity calculator and educational content have been developed by chemistry educators and laboratory professionals with extensive experience in analytical chemistry, solution preparation, and chemical education.
All formulas, calculations, and safety guidelines follow internationally recognized chemistry standards and best laboratory practices.
Our molarity calculator uses internationally recognized chemistry standards and formulas from: