Molar Mass Calculator

Calculate the molar mass of chemical compounds with our free calculator. Supports complex formulas and provides detailed element breakdowns.

Calculate Your Molar Mass Calculator

For best results, use common formulas like H2O, CO2, NaCl, C6H12O6, etc.

Understanding Molar Mass

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It's a fundamental concept in chemistry that connects the microscopic world of atoms and molecules to the macroscopic world of measurable quantities.

A mole is a unit representing 6.022 × 10²³ (Avogadro's number) particles, which could be atoms, molecules, ions, or other entities. The molar mass allows chemists to convert between the mass of a substance and the number of moles.

How to Calculate Molar Mass

The molar mass of a compound is calculated by adding up the atomic masses of all atoms in the chemical formula:

  1. Identify all elements in the chemical formula
  2. Determine how many atoms of each element are present in one molecule
  3. Multiply the atomic mass of each element by the number of atoms
  4. Sum all these values to get the total molar mass

Example: Calculating the molar mass of H₂O (water)

  • Hydrogen (H): 2 atoms × 1.008 g/mol = 2.016 g/mol
  • Oxygen (O): 1 atom × 15.999 g/mol = 15.999 g/mol
  • Total molar mass: 2.016 + 15.999 = 18.015 g/mol

Applications of Molar Mass

  • Stoichiometry: Calculating the quantities of reactants and products in chemical reactions.
  • Solution Preparation: Determining the mass of solute needed to prepare a solution of a specific molarity.
  • Gas Laws: Converting between mass and volume of gases under different conditions.
  • Colligative Properties: Calculating freezing point depression, boiling point elevation, and osmotic pressure.
  • Chemical Analysis: Determining the empirical and molecular formulas of compounds.

Common Conversion Formulas

Converting mass to moles:

Number of moles = Mass (g) ÷ Molar mass (g/mol)

Converting moles to mass:

Mass (g) = Number of moles × Molar mass (g/mol)

Converting moles to number of particles:

Number of particles = Number of moles × Avogadro's number (6.022 × 10²³)

See Also

Related Calculators

Atomic Mass Calculator

Calculate the atomic mass of elements

Average Atomic Mass Calculator

Calculate average atomic mass from isotope abundances

Atom Calculator

Calculate atomic properties based on atomic number and mass

Grams to Moles Calculator

Convert between mass in grams and amount in moles for chemical substances.

Frequently Asked Questions

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). One mole contains exactly 6.022 × 10²³ (Avogadro's number) particles, which could be atoms, molecules, or formula units. For example, the molar mass of water (H₂O) is 18.015 g/mol, meaning that 18.015 grams of water contains one mole of water molecules.

To calculate the molar mass of a compound:

  1. Identify all elements in the chemical formula
  2. Look up the atomic mass of each element from the periodic table
  3. Multiply the atomic mass of each element by the number of atoms of that element in the formula
  4. Add all these values together to get the total molar mass

For example, to calculate the molar mass of H₂SO₄:

  • H: 2 atoms × 1.008 g/mol = 2.016 g/mol
  • S: 1 atom × 32.065 g/mol = 32.065 g/mol
  • O: 4 atoms × 15.999 g/mol = 63.996 g/mol
  • Total molar mass: 2.016 + 32.065 + 63.996 = 98.077 g/mol

These terms are related but have distinct meanings:

  • Atomic mass is the mass of a single atom, measured in atomic mass units (amu) or daltons (Da). It represents the weighted average of all naturally occurring isotopes of an element.
  • Molecular mass (or molecular weight) is the sum of the atomic masses of all atoms in a molecule, also measured in amu or Da. It represents the mass of a single molecule.
  • Molar mass is the mass of one mole (6.022 × 10²³ particles) of a substance, expressed in grams per mole (g/mol). Numerically, the molar mass in g/mol equals the molecular mass in amu, but they have different units.

Molar mass is crucial in chemistry because it serves as a bridge between the microscopic world of atoms and molecules and the macroscopic world of measurable quantities. It allows chemists to convert between mass (which can be measured on a balance) and the number of moles (which represents a specific number of particles). This conversion is essential for stoichiometric calculations in chemical reactions, preparing solutions of specific concentrations, analyzing chemical compositions, and applying gas laws. Without molar mass, it would be impossible to predict or interpret the quantitative aspects of chemical processes.

When calculating the molar mass of compounds containing polyatomic ions, treat the polyatomic ion as a group of atoms that appears multiple times in the formula, based on the subscripts.

For example, to calculate the molar mass of Ca(NO₃)₂:

  • Ca: 1 atom × 40.078 g/mol = 40.078 g/mol
  • N: 2 atoms × 14.007 g/mol = 28.014 g/mol
  • O: 6 atoms (3 in each NO₃ group × 2) × 15.999 g/mol = 95.994 g/mol
  • Total molar mass: 40.078 + 28.014 + 95.994 = 164.086 g/mol

The key is to account for all atoms in the formula, including those within the polyatomic ion, and to consider how many times the polyatomic ion appears in the formula.

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