Ethanol-Water VLE Calculator

Student: Enriquez Palma

Creation date: September 8, 2026

System: Ethanol (component 1) + Water (component 2)

Total pressure: 1 atm = 101.325 kPa = 760 mmHg

Purpose

This app calculates the missing two equilibrium variables when one of the following is supplied: liquid ethanol mole fraction x, vapor ethanol mole fraction y, or temperature T.

The equilibrium data are represented with a dense table using a step of 0.001 in x, obtained by linear interpolation between the tabulated ethanol-water VLE data at 1 atm.

How to use

1. Select whether the known variable is x, y, or T.
2. Enter its value in the corresponding field.
3. Press Calculate.
4. The program reports the missing equilibrium variables.

Mole fractions are dimensionless. Temperature must be entered in °C.

Calculation

Known variable Liquid mole fraction x Vapor mole fraction y Temperature T (°C)

x

Mathematical basis

The app uses the VLE relationship represented by the experimental ethanol-water equilibrium data:

\(T=f(x),\qquad y=g(x)\)

For a supplied x, interpolation directly provides y and T. For a supplied y, the program searches the dense table for the corresponding x and T. For a supplied T, the program searches for all crossings of the temperature curve and reports every equilibrium solution when the ethanol-water azeotrope produces more than one composition at the same temperature.

Reference data

The base data correspond to ethanol-water VLE at 1 atm, with x and y as mole fractions of ethanol. The original tabulated points are shown below; the calculator internally uses a 0.001 x-step interpolation.

x ethanol	y ethanol	T (°C)

Reference: Wankat, Separation Process Engineering, ethanol-water VLE data at 1 atm (Table 2-1), as reproduced in public technical sources.