Molar mass calculator

The molar mass calculator quickly determines the molar mass and the percentage mass composition of a substance bases upon it's chemical formula. It uses the relative atomic weights of the elements. The calculator is found on the right hand side panel of this page.

What is Molar mass?

A mole is a quantity that chemists use in calculations involving mass, volume, concentration and number of particles. One mole has been defined as the number of atoms in excactly 12 grams of Carbon-12. This number very large and is approximately 6.022 x 10²³

The molar mass of a chemical species is defined as the number of grams that one mole of a chemical weighs. The units for molar mass are g mol^-1 or grams per mole.

The molar mass is calculated by adding up the relative atomic weights of each element in a chemical species according to the chemical formula of that species. The term 'formula mass' is often used instead of molar mass.

Molar mass calculations

Let

Ar = relative atomic weight of an element.

The relative atomic weights of the elements can be found on a Periodic Table

M = molar mass of a chemical species in g mol^-1 or g/mol

Calculate the molar mass of the following chemical substances.

1. Water, H₂O

M(H₂O) = 2 x Ar(H) + 1 x Ar(O)

M(H₂O) = 2 x 1.00794 + 1 x 15.9994

= 18.0153 g mol^-1

2. Oxygen, O₂

M(O₂) = 2 x Ar(O)

M(O₂) = 2 x 15.9994

= 31.9988 g mol^-1

3. Sodium chloride, NaCl

M(NaCl) = 1x Ar(Na) + 1 x Ar(Cl)

M(NaCl) = 1 x 22.98976928 + 1 x 35.453

= 58.4428 g mol^-1

4. Glucose, C₆H₁₂O₆

M(C₆H₁₂O₆) = 6 x Ar(C) + 12 x Ar(H) + 6 x Ar(O)

M(C₆H₁₂O₆) = 6 x 12.0107 + 12 x 1.00794 + 6 x 15.9994

M(C₆H₁₂O₆) = 180.1559 g/mol

5. Sulfuric acid, H₂SO₄

M(H₂SO₄) = 2 x Ar(H) + 1 x Ar(S) + 4 x Ar(O)

M(H₂SO₄)) = 2 x 1.00794 + 1 x 32.065 + 4 x 15.9994

M(H₂SO₄)) = 98.0785 g/mol