Normally you know what prac it is going to be or the pracs from which they are going to choose. To study for a practical exam it is slightly different from a normal exam.
You want to know things like:
- what are the common safety risks associated with the chemicals or equipment you are using? how can you minimise these risks? (for this saying things like wear safety glasses, lab coat and gloves is okay but you should have more specific things as well. For example if you are working with a chemical that is an acid you might say something like have a neutralising agent available in case of a spill. You can also talk about other minor risks like a glass breaking and say something like keep it away from the edges of the bench and if broken or chipped do not use)
- the method
- variables: independent, dependent, controlled
- aim
- hypothesis
- how you will summarise your results i.e. a table? do you need to draw any graphs, are there any calculations involved for that practical that you need to be familiar with
- discussion basics: e.g. is the experiment accurate, was it reliable, is it valid. Providing improvements to all those things as well because they usually ask about that.
- conclusion
Those are usually the things tested in a practical exam. If the practical has more theory to do with it, which in this case is likely because you do the equilibrium experiment and get for example a colour change when you increase the temperature or add something to the equilibrium. You will need to be able to justify using Le Chatelier's principle and/or collision theory for how these changes take place and why you see that certain colour.
In terms of actually performing the prac this one should be fairly easy and it will more so focus on the analysis vs something like titration practicals where the actual way you perform the practical is important.