Empirical Formula Calculator Formula

Understand the math behind the empirical formula calculator. Each variable explained with a worked example.

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Formulas Used

Moles of A

moles_a = mass_a / atomic_mass_a

Moles of B

moles_b = mass_b / atomic_mass_b

Ratio of A (divide by smallest)

ratio_a = (mass_a / atomic_mass_a) / ((mass_a / atomic_mass_a) < (mass_b / atomic_mass_b) ? (mass_a / atomic_mass_a) : (mass_b / atomic_mass_b))

Ratio of B (divide by smallest)

ratio_b = (mass_b / atomic_mass_b) / ((mass_a / atomic_mass_a) < (mass_b / atomic_mass_b) ? (mass_a / atomic_mass_a) : (mass_b / atomic_mass_b))

Variables

VariableDescriptionDefault
mass_aMass of Element A(g)40
atomic_mass_aAtomic Mass of A(g/mol)12.011
mass_bMass of Element B(g)6.7
atomic_mass_bAtomic Mass of B(g/mol)1.008

How It Works

How to Find the Empirical Formula

Steps

1. Convert mass of each element to moles: moles = mass / atomic mass 2. Divide each by the smallest number of moles 3. Round to the nearest whole number to get subscripts

Worked Example

A compound has 40 g C and 6.7 g H.

mass_a = 40atomic_mass_a = 12.011mass_b = 6.7atomic_mass_b = 1.008
  1. 01Moles C = 40 / 12.011 = 3.33
  2. 02Moles H = 6.7 / 1.008 = 6.65
  3. 03Divide by smallest (3.33): C = 1, H = 2
  4. 04Empirical formula: CH2

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