Raoult's Law Calculator

Raoult's Law Calculator | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Science & Education
Input types: select, number
Output type: text
Sample coverage: 4
API ready: Yes

Overview

The Raoult's Law Calculator computes partial vapour pressures, total mixture vapour pressure, and vapour-phase mole fractions for ideal solutions. Whether evaluating vapour pressure lowering from non-volatile solutes or analyzing binary liquid mixtures for distillation separation, it delivers exact thermodynamic calculations instantly.

When to use

Calculating total vapour pressure and vapour-liquid equilibrium compositions for binary ideal mixtures.
Evaluating vapour-pressure lowering caused by non-volatile solutes dissolved in a pure solvent.
Estimating top-vapour component enrichment when designing or modeling distillation columns.

How it works

1Select your calculation mode: single component for solvent vapour lowering, or binary mixture for two-component equilibrium.
2Input the liquid-phase mole fraction (x or x_A) and pure-liquid vapour pressures (p* or p_A* and p_B*) at your operating temperature.
3The tool applies Raoult's law (p_i = x_i · p_i*) and Dalton's law to calculate partial pressures, total pressure, and vapour-phase mole fractions.

Use cases

Chemical engineering students solving physical chemistry equilibrium and distillation problem sets.
Process technicians modeling binary solvent separation across fractional distillation stages.
Laboratory researchers predicting solvent evaporation rates and colligative properties in solute solutions.

Examples

1. Benzene-Toluene Binary VLE Calculation

Chemical Engineering Student

Background

Analyzing an equimolar benzene-toluene distillation feed at 25 °C in an equilibrium separation lab.

Problem

Determine the total vapour pressure and the vapour-phase mole fraction of benzene to verify volatility enrichment.

How to use

Select 'Binary mixture' mode, set x_A to 0.5, enter pure benzene vapour pressure (95.1 torr) for p_A*, and toluene (28.4 torr) for p_B*.

mode: binary, xA: 0.5, pAStar: 95.1, pBStar: 28.4

Outcome

Yields partial pressures p_A = 47.55 torr and p_B = 14.2 torr, total pressure p = 61.75 torr, and vapour fraction y_A = 0.77.

2. Aqueous Solution Vapour Pressure Lowering

Formulation Chemist

Background

Formulating a water-based mixture containing dissolved non-volatile solutes at 25 °C where water mole fraction drops to 0.85.

Problem

Calculate the resulting vapour pressure and determine the absolute vapour-pressure lowering compared to pure water.

How to use

Select 'Single component' mode, enter water mole fraction x = 0.85, and set pure water vapour pressure p* = 23.76 torr.

FAQ

What is Raoult's law?

Raoult's law states that the partial vapour pressure of a component in an ideal solution is equal to its liquid mole fraction multiplied by its pure-component vapour pressure.

How is vapour-phase composition calculated?

Using Dalton's law alongside Raoult's law, the vapour mole fraction of component A is computed as y_A = p_A / p_total.

What pressure units can I use?

You can use any pressure unit (such as torr, mmHg, kPa, or bar) as long as you input all pure-component vapour pressures in the same unit.

What does single component mode calculate?

It calculates the lowered vapour pressure of a solvent containing a non-volatile solute and reports the total vapour-pressure drop (Δp = (1 - x) · p*).

When does a liquid mixture follow Raoult's law?

A mixture follows Raoult's law when intermolecular forces between dissimilar molecules are similar to those between like molecules, behaving as an ideal solution.

mode: single, x: 0.85, pStar: 23.76

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Benzene-Toluene Binary VLE Calculation

2. Aqueous Solution Vapour Pressure Lowering

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