Make sure your question interpretation is impeccable, that's what killed me in Chem =D
The one really annoying thing in Chem exams is all those 1 mark random theory questions that come out of nowhere, e.g. "Why is ammonia better produced onsite rather than at a distant location?" or something like that.
If you want a 50, try not wanting a 50. Excellence in a field does not come from wanting a score, it comes from innate and tireless passion.
=/ I wanted 50 in Spesh the whole year, I even made an FB status about itl ike 2 months before exams lmao. And I was not passionate about Physics, I decided for Unit 4 to not spend time learning all the extra material that was unrelated to the exams, such as the inner-working of diodes for Unit 3.