# Why is k constant in Boyle's law?

##### 1 Answer

Boyle's law was first formulated as an experimental gas law which described how the pressure of a gas decreased when the volume of said gas increased.

A more formal description of Boyle's law states that the pressure exerted by a mass of ideal gas is inversely proportional to the volume it occupies **if** temperature and amount of gas remain unchanged.

Mathematically, this can be written as

This is where a

This can be easily derived from the ideal gas law,

We need to keep the amount of gas, which represents the number of moles, and the temperature constant. Since

Therefore,