Before I answer, your example sentence isn't grammatical English. It should be:
This person got an exemption from the basic chemistry course.
However, I don't think a native speaker would use "exemption" here. To be exempt from something, that something needs to be a requirement, which the chemistry course isn't. The requirement in this case would be taking the course. I think it would also be more natural to use the verb to exempt in this context:
This person was exempted from taking the basic chemistry course.
This sentence sounds more natural, but still isn't what I would expect a native speaker to say. I don't think there's a good reason for this, other than there being more specific terms used in this context.
J.R.'s answer provides some good examples of what a native speaker might say:
- Because you took it already, we can waive your basic chemistry course
requirement.
- We can transfer your chemistry credits, so you won't have to take that
course again.
- We can apply the chemistry credits you earned at your last
school.‡
- If you score high enough, you can test out of the chemistry course.
‡ Note that use of "school" to describe a university (or college) is primarily an American usage. In British English, it would only be referred to as a university, and it would only ever be a university which could
grant a degree.
There is an exception to the rule, however. If the module was not optional for students who hadn't already taken it, a lecturer or professor might use "exempt" when describing the module:
This module is mandatory. Students who have already gained the module
are exempt.