Eco essays , one way of preparing for them is knowing your syllabus well/having up to date and important stats. Also, just write alot of essays plans!! Look at the possible questions they can ask for you and make a generic plan for it for the HSC.
EG. A generic
essay on monetary policy
-include DMO and RBA'S role
-How interest rates will effect the economy (transmission mechanism)
Conquering Chemistry is the most popular chem textbook for Year 11 and Year 12 and is pretty good at theory parts.
However, I think Jarcaranda Chemistry (which is newer) is more thorough and sp I think it's good to have both Conquering Chemistry and Jarcaranda Chemistry and use them together.