How can tell you whether there is a particular compound or element in a product of a reaction?

In a heat of an engine, if 700 j enters the system, and the piston does 400 j of work what is the final internal (thermal) energy of the system if the initial energy is 1,500 j

If 3 moles of a compound use 24 j of energy in a reaction, what is the a hreaction in j/mol?

Δu of , in kj/kg, as it isto k, (a)as a of , (b) at , (c) at .