Chemistry is often considered to be a “complicated” subject that is “only for smart people”. Studying Chemistry indeed requires the interest, commitment and practice, however we here at The Zen of Chemistry believe that ANYONE can learn chemistry, given the right tools. In chemistry one needs to be able to use equations and calculate answers, and in order to do this, being able to rearrange equations to find the desired value is a key skill. Rearranging equations comes easily to those with a strong maths/algebra background, however for some of us, our creative and visual brains just don't work that way, and we need different tools to get the job done. We're here to tell you THERE IS AN EASIER WAY!(PS: If you'd prefer to watch a video, watch it here) |

A lot of people love the equation triangles however they get stuck when they have to use equations like PV=nRT. Our solution lies in other equation shapes, like trapezii and squares, however they do come with a warning, they are slightly harder to use. But that's ok! Once you know how, it'll be an absolute breeze!!The same rules apply - horizontal lines correspond to division and vertical lines correspond to multiplication. |

The one rule that changes with shapes other than triangles, is that you can only select your desired variable from the bottom row.As you can see from the diagram on the right for PV=nRT, there are two trapezii to choose from. Depending on which variable you wish to determine, will depend on which trapezii you will use. |

**If you wish to determine n, R or T, you would use the top trapezium, as these variables are on the bottom.**

**If you wish to determine P or V, you would use the bottom trapezium.**

The five equations derived from this trapezii are:

The same goes for equation squares and other equations:

**Extension: PV=nRT and the other gas laws**

**The good news: There's no need to remember them all!**

Here's how you do it:

Here's how you do it:

- Make two PV=nRT trapezii equal one another:

- Cross out the variables which stay the same in the experiment. In the example we have used here, the variables V, n and R are constant.

- The variables on the left are now your initial values (denoted by i), and the variables on the right are now your final values (denoted by f).

- If you have no fraction (e.g. PiVi = PfVf), you are finished! Create your two equation squares and proceed to calculate away!

- If you have a fraction, as per this example, move the bottom terms up to the top on the opposite side of the equals sign and multiply them by what's already there.

- Create your two equation squares and proceed to calculate away!

**Our exam tip: If you have trouble remembering equation shapes, what many of our students do is quickly draw them up as soon as writing time begins. This may take you a couple of minutes in total, but you'll be drawing them up while your mind is fresh, and it is likely to save you time in the long run.**

## About the Author

Amelia has been a Chemistry Educator since 2002, and is passionate about making learning simple. She believes that ANYONE can learn ANYTHING they want if they have the drive and interest and are willing to do the hard yards.

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