Can i still do this with Chem
it depends because if you have maths it will be much better. The subject combinations would match and universities would look for students who do related subjects to gain the skills beneficial for the degree. For example, my A levels are Maths, Economics, and History.
AS level begins with stuff like index laws and expanding brackets (seriously).
There is a lot of overlap with GCSE content.
AS -> A2 is a bigger jump, but keep on top of your work and you will be just fine.