Mole Fraction Calculator Formula
Understand the math behind the mole fraction calculator. Each variable explained with a worked example.
Formulas Used
Mole Fraction of A
fraction_a = moles_a / (moles_a + moles_b)Mole Fraction of B
fraction_b = moles_b / (moles_a + moles_b)Variables
| Variable | Description | Default |
|---|---|---|
moles_a | Moles of Component A(mol) | 2 |
moles_b | Moles of Component B(mol) | 3 |
How It Works
How to Calculate Mole Fraction
Formula
X_A = n_A / (n_A + n_B)
Mole fractions are dimensionless and always sum to 1.
Worked Example
A mixture of 2 mol ethanol and 3 mol water.
moles_a = 2moles_b = 3
- 01Total moles = 2 + 3 = 5
- 02X_A = 2 / 5 = 0.4
- 03X_B = 3 / 5 = 0.6
Frequently Asked Questions
What is mole fraction?
Mole fraction is the ratio of moles of one component to the total moles in the mixture. It ranges from 0 to 1.
Why must mole fractions sum to 1?
Because they represent proportions of the whole mixture.
How is mole fraction related to partial pressure?
By Dalton's law, partial pressure of a gas equals its mole fraction times total pressure: P_i = X_i × P_total.
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Open Mole Fraction Calculator