2 NO(g) + O2 (g) <==> 2 NO2 (g)

Question

Given that Kp=7.96×1012 for the reaction above and the following starting conditions:

Initial Concentrations
p(NO)=0.775 atm
p(NO2)=0.000 atm
p(O2)=0.789 atm

Determine the equilibrium concentration of NO2.

Answer 1

........2NO + O2 ==> 2NO2
I.....0.775.0.789....0
C.......2x....-x.....2x
E..0.775-2x.0.789-x..2x

Substitute the E line into Kp expression and solve for x then evaluate the individual pressures.
I should point out that I did NOT work this problem as concentrations since you gave the pressures in atm for initial conditions but called them concns. I think you must have meant pressures. And you gave a Kp also. With no T listed you can't evaluate Kc.