Whenever you get a question wrong, you need to make sure you get to the bottom of what specific mistake you’re actually making so that you can work on it.

In this video lesson, you’ll see how a simple mistake with an A-level Chemistry calculation can have more than one cause, and how you’ll need to take a different course of action to improve, depending on what it is that you’re doing wrong.

Summary of video: When you do an amount of substance calculation and get it wrong, it’s not necessarily your knowledge of moles calculations that’s the problem. It might be that you’re just assuming that all reactants and products are present in a one-to-one ratio (super common mistake). To solve this problem, you need to write out a full balanced equation for the reaction that’s taking place so you can see what the mole ratio is and factor it in to the calculation. Another explanation for the mistake in the video is remembering to think about the stoichoimetry, but balancing the equation wrong. If this is what you’re doing, the course of action you’d take is practicing balancing equations.