Exam revision question. Help!! Hello. I have a thermodynamics exam tomorrow. This is a past exam question and i'm not doing very well with it. If anyone has any ideas please help!! A charge enters a spark ignition engine at 330K and 1 bar, and is isentropically compressed through a ratio of 7:1. Estimate the temp and pressure at the end of the compression, taking the charge to be: a) pure air with constant specific heat. b) a stoichiometric mixture of air and octane(C8H18) with variable specific heats (neglect residual gases).