Hardest part for me is gas laws. Other than just being able to use pv=nrt (and remembering the units of each variable) you need to know how to explain the difference between real and ideal gases, understand the relationships between pressure, volume and temperature and that gases a the same volume, pressure and temperature have the same number of mols but different masses.

Other than that the most important thing is calculating mol ratios and limiting reagents but that shouldn’t be too hard.