Is the Chem 1A03/1AA3 Mastering chemistry access code useful?

wait for the first day of class. if its still a mark booster then do it. it is definitely useful as an introductory practice, but the bulk of your study material before midterms/exams will be the past tests posted on avenue.

I heard last year it could count towards 6% of your chemistry mark. Not sure if they're doing it this year.

Yes, last year Mastering Chem counted towards 6% of the mark, but it was optional in the second term. I would recommend you buy it, anyhow. It's extremely easy, and if you get an aggregate of 100%+ marks, you get marks over that 6% too! (You can get over 100% per question because of bonus marks).

It really walks you through the stuff and makes it easier to understand. Even if you didn't, you can see where you went wrong and stuff.