Empirical Formula Calculator Formula
Understand the math behind the empirical formula calculator. Each variable explained with a worked example.
Formulas Used
Moles of A
moles_a = mass_a / atomic_mass_aMoles of B
moles_b = mass_b / atomic_mass_bRatio 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
| Variable | Description | Default |
|---|---|---|
mass_a | Mass of Element A(g) | 40 |
atomic_mass_a | Atomic Mass of A(g/mol) | 12.011 |
mass_b | Mass of Element B(g) | 6.7 |
atomic_mass_b | Atomic 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.
- 01Moles C = 40 / 12.011 = 3.33
- 02Moles H = 6.7 / 1.008 = 6.65
- 03Divide by smallest (3.33): C = 1, H = 2
- 04Empirical formula: CH2
Frequently Asked Questions
What is an empirical formula?
The simplest whole-number ratio of atoms in a compound. For example, glucose (C6H12O6) has empirical formula CH2O.
How is empirical different from molecular?
The molecular formula is a whole-number multiple of the empirical formula. You need the actual molar mass to find which multiple.
What if the ratios are not whole numbers?
Multiply all ratios by the smallest integer that makes them whole. For example, 1:1.5 becomes 2:3.
Ready to run the numbers?
Open Empirical Formula Calculator