we use Chem in a focus at school, and I supplement with Strive + atar notes but was wondering if there’s a textbook/source that has really difficult chem questions??
The Chemistry Olympiad has some good questions if I recall correctly. (https://www.asi.edu.au/programs/past-exams/chemistry-olympiad-past-exams). Just pick and choose relevant questions which cover HSC content, as I'm pretty sure some of the paper is Year 11 content (still might be useful though).
we use Chem in a focus at school, and I supplement with Strive + atar notes but was wondering if there’s a textbook/source that has really difficult chem questions??
Do questions from trial papers. The above with the olympiad although they may be harder than HSC, in my opinion it's not a good way to study for the subject in terms of the HSC. In the olympiad exams the questions are more problem focused, with not that much writing involved. HSC exams there is a lot of writing and explaining content so the best way to prepare for this is through trial exam papers. You can find those on websites like THSConline
The olympiad questions can be used but only as a means to improve your skills in calculations and more problem based questions