Calculadora de Fração Molar
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
x_A = n_A / (n_A + n_B)
About this calculator
The Mole Fraction Calculator determines the mole fraction of a component in a binary mixture using the formula x_A = n_A / (n_A + n_B), where n_A and n_B are the amounts of substance (in moles) of components A and B. The mole fraction is dimensionless and ranges from 0 to 1, representing the proportion of moles of A relative to the total.
To use the calculator, enter the values of n_A and n_B in the corresponding fields. The result is displayed immediately, with up to 4 decimal places. This tool is useful for chemistry students, engineers, and professionals needing to calculate mixture compositions in solutions, reactions, or industrial processes.
Mole fraction is widely applied in gas laws, vapor pressure, equilibrium constants, and colligative properties. For example, when calculating the partial pressure of a gas in a mixture (Dalton's Law), mole fraction is essential. Caution: ensure you use moles, not mass or volume, as input.
The calculator works only for binary mixtures. For mixtures with more components, the formula extends to x_i = n_i / Σ n_j. Verify that mole values are positive; zero or negative inputs cause errors. Always check that units are consistent.
Frequently asked questions
What is mole fraction?
Mole fraction is the ratio of the number of moles of a component to the total number of moles in the mixture. It is a dimensionless concentration measure ranging from 0 to 1.
How to calculate mole fraction with more than two components?
For multiple components, use x_i = n_i / (n_1 + n_2 + ... + n_k). This calculator is for binary mixtures; for more components, sum all moles in the denominator.
Can I use mass instead of moles?
No. Mole fraction requires amounts in moles. If you have mass, convert to moles using molar mass before entering into the calculator.
What happens if I enter zero for one component?
If n_A = 0, the mole fraction of A is 0. If n_B = 0, the mole fraction of A is 1 (provided n_A > 0). If both are zero, the calculation is undefined (division by zero).
Can mole fraction be greater than 1?
No. The mole fraction of a component in a mixture is always between 0 and 1, inclusive. The sum of mole fractions of all components equals 1.