Molarity Calculator

About Molarity

Molarity (M) is a unit of concentration representing the number of moles of solute per liter of solution. It is one of the most commonly used units for measuring concentration in chemistry.

Understanding Molarity

The formula for molarity is:

Molarity (M) = moles of solute / liters of solution

Key concepts:

• Solute: The substance being dissolved (usually a solid)
• Solvent: The substance doing the dissolving (usually a liquid, often water)
• Solution: The homogeneous mixture of solute and solvent
• Mole: A unit of measurement for amount of substance (6.022 × 10²³ particles)

When to Use This Calculator

This calculator is useful for:

• Preparing solutions of known concentration
• Determining the concentration of an existing solution
• Calculating dilutions to achieve desired concentrations
• Converting between mass and moles of a substance
• Chemistry lab work and experiments

Example Calculations

Example 1: What is the molarity of a solution made by dissolving 58.44 grams of NaCl in 1 liter of water?

Molecular weight of NaCl = 58.44 g/mol
Moles of NaCl = 58.44 g / 58.44 g/mol = 1 mole
Molarity = 1 mole / 1 L = 1 M

Example 2: How many grams of glucose (C₆H₁₂O₆) are needed to make 500 mL of a 0.5 M solution?

Molecular weight of glucose = 180.16 g/mol
Moles needed = 0.5 M × 0.5 L = 0.25 moles
Mass needed = 0.25 moles × 180.16 g/mol = 45.04 grams

Dilution Calculations

The dilution equation is:

M₁V₁ = M₂V₂

Where:
M₁ = initial concentration
V₁ = initial volume
M₂ = final concentration
V₂ = final volume

This equation shows that the product of molarity and volume before dilution equals the product of molarity and volume after dilution.