What is matter and how does it work

Given the following at 25c calculate delta hf for hcn (g) at 25c. 2nh3 (g) +3o2 (g) + 2ch4 (g) > 2hcn (g) + 6h2o (g) delta h rxn= -870.8 kj. delta hf=-80.3 kj/mol for nh3 (g), -74.6 kj/mol for ch4, and -241.8 kj/mol for h2o (g)

Balance the following reaction. as2s3 + 9o2 → 2as2o3 + so2

Is of of 3- ? a. 1--3- b. 1--2- c. 1--3- d. of