Digging through my brain for some Inorganic Chemistry knowledge

I'm currently feeling a little bit ignorant or as I may say, incompetent, to take the last inorganic Chem class. All the information that I've collected from the past two classes that I took are gone from my head. I felt so depressed when I looked at a question about "finding the final concentrations of all ions" in a pre-lab today, because I completely forgot the whole concept of concentration stoichiometry. SO SAD. I guess I have to start racking up those old notes from my first two Inorganic Chem class. Hopefully, I did not throw anything out.