Molar Mass and Empirical Formulas in Chemistry

Mole

Counting number; 1 mol = 6.02 × 10²³ items.

Avogadro's Number

6.02 × 10²³ items per mole.

Molar Mass

Mass of 1 mole of a substance in g/mol.

Atomic Mass

Mass of an atom in atomic mass units (amu).

Empirical Formula

Smallest whole number ratio of atoms in a compound.

Molecular Formula

Actual number of atoms in a molecule.

Percent Composition

Percentage by mass of each element in a compound.

Example of Empirical Formula

C2H6 reduces to CH3.

Example of Empirical Formula Calculation

Find empirical formula from mass percentages.

Molar Conversion

Convert between mass (g) and moles (mol).

Hydrate

Compound with water molecules in its structure.

Anhydrous

Substance without water.

Molar Mass of Water

18.02 g/mol for H2O.

Molar Mass of Carbon

12.01 g/mol for carbon.

Molar Mass of Aluminum

26.98 g/mol for aluminum.

Molar Mass of Zinc

65.39 g/mol for zinc.

Molar Mass of Diphosphorus Pentoxide

141.94 g/mol for P2O5.

Molar Mass of Sodium Sulfate

Molar mass calculation for Na2SO4.

Molar Mass of Calcium Phosphate

Molar mass calculation for Ca3(PO4)2.

Percent Composition Calculation

Mass of element / total mass × 100.

Subscript Reduction

Reduce subscripts to find empirical formula.

Molecular Mass

Mass of a molecule in g/mol.

Percent Water in Hydrate

Water mass / total mass × 100.

Example of Molecular Formula

C2H6 is molecular formula for ethane.

Hydrate Naming

Naming convention for compounds with water.

Percent Composition of Cu2S

79.84% Cu and 20.14% S.

Molar Mass of Calcium Chloride Dihydrate

Molar mass calculation for CaCl2·2H2O.

Example of Molar Conversion

26 g C = 2.2 mol C.