No, not that one… the other one. By mole we mean a unit used in chemistry to express how much of a substance you have. In this section, we will learn how to calculate moles, and use moles to calculate other quantities.    

We’re going to use formula triangles to present the formulae instead of the normal way – it’s easier.

 If you’ve never seen or used a formula triangle they may look scary. All you need to do is cover up what you want and then look at what you have left. What you do with the two things you have left is summarised in this diagram (we’ve used numbers so you can see it in action):

 So, if we look at the diagram very briefly. If you cover up the one it leaves you with two 2s. On the arrow we have a divide sign. Follow the instruction and you get 1 (2÷2 = 1).           

Right, now that we’ve got to grips with formula triangles we can now get to grips with calculating moles and co.     

Were going to do three examples:

Partially Insane Ira (Betty and Ron’s son) has 50 grams of sodium chloride. How many moles does it contain?

 Now that we have the GFM of chlorine we can look at the triangle again. We will use the one on the left. The formula we use is:

 Now substitute in what you know and do the calculation: