For chemistry majors, math is really needed only for understanding physical chemistry. However, if you are going for a degree in chemistry, you will need to take physical chemistry courses, and therefore will need the math for those classes. However, for the physical chemistry courses that a regular chem major would take, all you really need to understand are differentials and how to perform some basic integrations (i.e. up to lower-division multi-variable calculus). However, if you take more advanced physical chemistry courses you'll need to understand more complex topics from linear algebra, group theory, and differential equations.