Isentropic relation between pressure and temperature – V.MohanKumar

Isentropic relation between pressure and temperature

(Wikipedia)

isentropic process: it is a thermodynamic process in which the entropy remains constant where there is no heat and mass transfer taking place. It is also called as a reversible adiabatic process. 

From the above formula, one can calculate the pressure P2 value after the reaction takes place in a process.