Molar Concentration Calculator
Calculate molarity (mol/L), moles, mass of solute, or volume of solution — solve for any variable in the molarity formula.
Concentration Result
Molar Concentration (Molarity)
Molarity is the most common way to express the concentration of a solution in chemistry. It tells you how many moles of solute are dissolved in one liter of solution.
The Formula
M = n / V
Where:
- M = Molarity in mol/L (written as M)
- n = Moles of solute
- V = Volume of solution in liters
Rearranging:
- n = M × V (moles = molarity × volume)
- V = n / M (volume = moles ÷ molarity)
Converting Between Moles and Grams
To find moles from mass, you need the molar mass (molecular weight) of the solute:
n = mass (g) / molar mass (g/mol)
mass = n × molar mass
Common Molar Masses
| Compound | Molar Mass (g/mol) |
|---|---|
| NaCl (table salt) | 58.44 |
| H₂O (water) | 18.02 |
| NaOH (sodium hydroxide) | 40.00 |
| HCl (hydrochloric acid) | 36.46 |
| H₂SO₄ (sulfuric acid) | 98.08 |
| Glucose (C₆H₁₂O₆) | 180.16 |
| NaHCO₃ (baking soda) | 84.01 |
| CaCO₃ (calcium carbonate) | 100.09 |
Standard Solution Concentrations
| Concentration | Use |
|---|---|
| 0.001 M (1 mM) | Trace analysis, enzyme assays |
| 0.1 M | Titration standard, buffer preparation |
| 1 M | Common lab stock solutions |
| 6 M | Concentrated acids in lab |
| 12 M | Near-maximum for HCl |
Preparing a Solution
- Calculate mass needed: mass = M × V × molar mass
- Weigh the solute accurately.
- Dissolve in about 80% of the target volume of solvent.
- Transfer to a volumetric flask and add solvent to exactly the target volume.
- Never add volume to solute — always add solute to solvent.
Safety Note
When diluting concentrated acids, always add acid to water — never add water to acid. The dissolution is exothermic and can cause violent spattering if water is added to acid.