The ideal gas equation.

All that is required to constuct and use the ideal gas equation.

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The breakdown of the equation.

The ideal gas equation is as follows:



With P being pressure, V is volume, n is the number of moles, R is the relative number and T is temperature.


The equation is made up of 2 smaller equations:

PV/T= Constant. And Constant= nR.

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Using the equation to work out moles.

Example question: A gas reaction took place at 400K at 20 Pa, in a container with the volume of 150 metres cubed. With the relative number of 8.314 JK mole to the power of minus 1. How many moles of gas were present?

We know the ideal gas equation so we can just minipulate it to work out n.

So PV=nRT now becomes n= RT/PV.

So we can now subsitute the numbers into the equation.

So n=8.314 x 400/20x150.

Which makes n to be 1.19 moles of gas to 2 decimal places.

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Common Pitfalls.

It is very important that you avoid some very common pitfalls. You can lose very simple marks because of the units being wrong (I have been guilty of this).

The units should aways be like this and if they aren't then you need to convert them prior to doing the calculation:

  • P = Pa or Nm-2
  • V = m3
  • N = moles
  • T = K






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