Molarity Calculator
Calculate the molarity of a solution, find the mass of solute needed, or determine the volume required to prepare a solution. Includes dilution calculations using the M₁V₁ = M₂V₂ formula. Perfect for chemistry students, lab professionals, and researchers.
What Is Molarity?
Molarity (M) is the most common unit of concentration used in chemistry. It is defined as the number of moles of solute dissolved in one liter of solution. The formula is:
M = n / V
Where:
M = Molarity (mol/L)
n = Number of moles of solute
V = Volume of solution (in liters)
The number of moles can be calculated from the mass of the solute and its molar mass:
n = m / MW
Where:
m = Mass of solute (in grams)
MW = Molar mass (g/mol)
This calculator helps you solve for any of these variables. Simply select the mode that matches what you want to find, enter the known values, and the calculator will compute the missing value.
Molarity vs Other Concentration Units
- Molarity (M): Moles of solute per liter of solution. Temperature-dependent.
- Molality (m): Moles of solute per kilogram of solvent. Temperature-independent.
- Normality (N): Equivalents of solute per liter of solution. Depends on reaction type.
- Mass Percent (% w/w): Mass of solute per mass of solution × 100.
- Parts Per Million (ppm): Mass of solute per million parts of solution.
Molarity is the most commonly used concentration unit in chemistry labs because it relates directly to the mole, which is the fundamental unit for chemical reactions.
Common Molar Mass Values (g/mol)
- NaCl: 58.44 (Sodium Chloride)
- HCl: 36.46 (Hydrochloric Acid)
- H₂SO₄: 98.08 (Sulfuric Acid)
- NaOH: 40.00 (Sodium Hydroxide)
- C₆H₁₂O₆: 180.16 (Glucose)
- C₂H₅OH: 46.07 (Ethanol)
- H₂O: 18.02 (Water)
- CO₂: 44.01 (Carbon Dioxide)
❓ Molarity Calculator FAQ
What is molarity?
Molarity (M) is the number of moles of solute per liter of solution. It is the most common unit of concentration used in chemistry. The formula is M = n / V, where n is the number of moles of solute and V is the volume of solution in liters.
What is the formula for molarity?
Molarity = Moles of Solute ÷ Volume of Solution (in liters). M = n / V. You can also calculate moles from mass: n = Mass ÷ Molar Mass.
How do I calculate molarity from mass?
First, calculate the number of moles: moles = mass ÷ molar mass. Then, divide by the volume in liters: molarity = moles ÷ volume.
How do I calculate the mass needed for a solution?
Mass = Molarity × Volume × Molar Mass. For example, to make 0.5 L of a 1 M NaCl solution, you need 0.5 × 1 × 58.44 = 29.22 g of NaCl.
What is the dilution formula?
The dilution formula is M₁V₁ = M₂V₂, where M₁ and V₁ are the concentration and volume of the stock solution, and M₂ and V₂ are the concentration and volume of the diluted solution.
How do I perform a dilution calculation?
Use the formula C₁V₁ = C₂V₂. If you know three of the four values, you can solve for the fourth. This calculator includes a dilution mode to do this for you.
What is the difference between molarity and molality?
Molarity is moles of solute per liter of solution (temperature-dependent). Molality is moles of solute per kilogram of solvent (temperature-independent). Molarity is more commonly used in lab work.
What is the difference between molarity and normality?
Molarity is moles of solute per liter of solution. Normality is equivalents of solute per liter of solution. Normality depends on the reaction type (e.g., acid-base, redox) and is not always equal to molarity.
What is the molar mass of NaCl?
The molar mass of NaCl (Sodium Chloride) is 58.44 g/mol (22.99 g/mol for Na + 35.45 g/mol for Cl).
How do I convert mL to L for molarity calculations?
Divide the volume in milliliters by 1000 to get liters. For example, 250 mL = 0.250 L. All molarity calculations require volume in liters.
How does temperature affect molarity?
Molarity is temperature-dependent because volume changes with temperature. As temperature increases, volume expands, so molarity decreases slightly. For precise work, solutions should be prepared and measured at a specific temperature.
What is a stock solution?
A stock solution is a concentrated solution that is diluted to prepare working solutions of lower concentration. Stock solutions are used to save time and ensure consistency in the lab.
What is the molarity of pure water?
Pure water has a molarity of approximately 55.5 M. This is calculated using the density of water (1 g/mL) and its molar mass (18.02 g/mol).
How do I calculate the volume needed for a dilution?
Use the dilution formula C₁V₁ = C₂V₂ and solve for the unknown volume. For example, to make 200 mL of 0.5 M solution from a 2 M stock, V₁ = (0.5 × 0.200) ÷ 2 = 0.050 L (50 mL).
What is the difference between solute and solvent?
The solute is the substance that is dissolved (e.g., salt). The solvent is the substance that does the dissolving (e.g., water). The combination of solute and solvent is called a solution.
How do I prepare a 1 M solution of NaCl?
Weigh 58.44 g of NaCl and dissolve it in enough water to make a total volume of 1 L. Use a volumetric flask for accurate volume measurement.
What is the relationship between molarity and pH?
For strong acids and bases, pH is directly related to molarity. For example, a 0.1 M HCl solution has a pH of 1. For weak acids and bases, the relationship is more complex and depends on the acid dissociation constant (Ka).
How does this calculator handle units?
This calculator uses grams for mass, liters for volume, and g/mol for molar mass. All volumes should be entered in liters. The calculator will display results in the appropriate units (mol/L, g, L, mol).
How accurate is this molarity calculator?
This calculator provides accurate results based on the standard formulas M = n/V and n = m/MW. However, actual laboratory measurements may vary due to temperature, purity of reagents, and measurement precision. Always use volumetric glassware for accurate solution preparation.
Can I use this calculator for acid-base titrations?
Yes, the molarity calculator can be used for acid-base titration calculations. You can calculate the concentration of an unknown solution using the relationship M₁V₁ = M₂V₂ at the equivalence point.