The vapor pressure calculator takes final pressure, final temperature, initial pressure, initial temperature, molar enthalpy of vaporization, mole fraction of the solvent and vapor pressure of the solvent and returns vapor pressure of the solution. It is built for quick answers, for checking somebody else’s arithmetic, and for the moments when a formula book is not within reach.
What Is the Vapor Pressure Calculator?
The vapor pressure calculator turns final pressure, final temperature, initial pressure, initial temperature, molar enthalpy of vaporization, mole fraction of the solvent and vapor pressure of the solvent into vapor pressure of the solution.
It is a quick way to get from the numbers you have to the number you need, without setting up a spreadsheet or reaching for a formula.
How the Vapor Pressure Works
Each result follows from the ones before it, and the calculator shows every step, so a surprising answer can be traced back to the input that caused it.
Round your inputs to the precision you actually know, and keep more precision than that in the intermediate steps.
Getting a Result You Can Trust
Run the calculation twice with slightly different inputs. A sensible calculator moves its output in proportion; a wild change points to a unit or a decimal point problem in what you entered.
Write the inputs down next to the answer. It takes a moment and it is the difference between a number you can explain and one you cannot.
A Worked Example
Working through an example, with final pressure set to 10, final temperature set to 5, initial pressure set to 2, the calculator returns vapor pressure of the solution of 10. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out vapor pressure of the solution?
Enter final pressure, final temperature, initial pressure, initial temperature, molar enthalpy of vaporization, mole fraction of the solvent and vapor pressure of the solvent. The calculator then works through the relationship and reports vapor pressure of the solution.
What does the vapor pressure actually calculate?
It takes final pressure, final temperature, initial pressure, initial temperature, molar enthalpy of vaporization, mole fraction of the solvent and vapor pressure of the solvent and converts them into vapor pressure of the solution using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter final pressure?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Does anything you type get stored?
No. The whole calculation runs inside your browser, and nothing you enter is uploaded, logged or sent anywhere.
Is the answer exact?
It is as exact as the formula and the inputs allow. The method itself is the standard one for this problem, so the only sources of error are the figures you enter and the precision you ask for.