Considering you come from a top 5 school, your chemistry exam will be much more difficult and the exams are set to challenge you. Getting a 56 is not the end of the world, I mean it isn't exactly a great mark but if you study hard and try your best for your next Chemistry assessments, a score in 75 in internals may positively affect your ranking. Generally your cohort will be pretty competitive and try to bring up each other's marks and reduce the gap between the marks so you must make sure you pull your weight and study hard!!!! You can use ATAR calculators to find out the scaling but I guess maybe an 80?? Im just making an estimate, make sure you improve yourself, do past papers and I'm sure you'll get a good overall HSC mark for Chemistryl Good Luck!