Quick Answer

0.5 moles of solute dissolved in 1.0 L of solution gives a molarity of 0.5000 M. Dissolving 58.44 g of NaCl (molar mass 58.44 g/mol) in 1 L yields a 1.0000 M solution.

Molarity (M = mol / L)

Solve For Molarity (M) Moles (mol) Volume (L)

Moles (mol)

Volume (L)

Mass and Volume to Molarity

Mass of Solute (g)

Molar Mass (g/mol)

Volume of Solution (L)

Common Examples

Input	Result
0.5 mol in 1.0 L	M = 0.5000 M
M = 2.0 M, V = 0.25 L	Moles = 0.5000 mol
0.1 mol, M = 0.5 M	V = 0.2000 L (200 mL)
58.44 g NaCl, molar mass 58.44 g/mol, 1 L	Molarity = 1.0000 M
40 g NaOH, molar mass 40 g/mol, 0.5 L	Molarity = 2.0000 M

How It Works

The Molarity Formula

M = n / V

Where:

• M = molarity in moles per liter (mol/L or M)
• n = moles of solute (mol)
• V = volume of solution in liters (L)

Rearranged:

• Moles: n = M x V
• Volume: V = n / M

From Mass to Molarity

When starting with a known mass of solute rather than moles:

M = (mass / molar mass) / V

First convert grams to moles by dividing by the molar mass, then divide by the volume in liters.

Molarity vs. Molality

Molarity (M) is moles of solute per liter of solution. Molality (m) is moles of solute per kilogram of solvent. Molarity changes with temperature because liquid volumes expand and contract. Molality does not change with temperature because mass is independent of temperature. For dilute aqueous solutions at room temperature, the values are nearly identical.

Common Molarities in the Lab

• Concentrated HCl: approximately 12 M
• Concentrated H2SO4: approximately 18 M
• Concentrated NaOH: approximately 19 M
• Saturated NaCl: approximately 6.1 M
• Typical lab dilute acid: 0.1 to 1.0 M

Worked Example

Dissolve 4.0 grams of NaOH (molar mass = 40.00 g/mol) in enough water to make 500 mL (0.5 L) of solution. Moles = 4.0 / 40.00 = 0.10 mol. Molarity = 0.10 / 0.5 = 0.20 M. The resulting solution is 0.20 M NaOH. To find how many moles are in 250 mL of this solution: n = 0.20 x 0.25 = 0.05 mol.

Related Calculators

Moles Calculator

Convert between mass, moles, and molar mass using the mole formula n = mass / molar mass.

Dilution Calculator

Calculate dilution volumes and concentrations using the C1V1 = C2V2 equation.

Frequently Asked Questions

What is molarity?

Molarity is a measure of concentration defined as the number of moles of solute dissolved per liter of total solution. It is denoted by M. A 1 M solution contains 1 mole of solute per liter of solution. It is the most commonly used concentration unit in chemistry.

What is the difference between molarity and molality?

Molarity (M) uses the volume of the solution as the denominator (mol/L), while molality (m) uses the mass of the solvent (mol/kg). Molarity is more convenient for measuring volumes in the lab, but molality is preferred for precise thermodynamic calculations because it does not vary with temperature.

Does molarity change with temperature?

Yes. Because molarity depends on volume, and liquids expand when heated, the molarity of a solution decreases slightly as temperature increases (same moles in a larger volume). For most practical purposes at room temperature, this effect is negligible, but it matters for precise analytical chemistry.

How do I convert mL to L?

Divide milliliters by 1,000 to get liters. For example, 250 mL = 0.250 L, 500 mL = 0.500 L, and 100 mL = 0.100 L. The molarity formula requires volume in liters, so always convert before calculating.

How do I find molar mass?

Molar mass is the sum of the atomic masses of all atoms in the molecular formula, expressed in grams per mole (g/mol). For example, NaCl has a molar mass of 22.99 (Na) + 35.45 (Cl) = 58.44 g/mol. The molar mass calculator on this site can compute this for any chemical formula.