What is the Kp?

Question

Some NOCl(g) at 1.0 atm is placed in an empty reaction vessel. At equillibrium, the total pressure is 1.135 atm. What is the Kp for the reaction below assuming partial pressures are in atmospheres?

Can someone help me out... thanks in advance!

2NOCl(g) --> 2NO(g) + Cl2(g)

Answer 1

.. .. .. .. .. .. 2NOCl <=> 2NO +Cl2
Initial .. .. .. .. 1
React .. .. .. .. 2x
Produce .. .. .. .. .. .. .. .. 2x .. .. x
At equil .. .. 1-2x .. .. .. .. 2x .. .. x

Kp= P(NO)^2 *P(Cl2)/P(NOCl)^2 = (2x)^2 *x/(1-2x)^2 =>
Kp= 4x^3/(1-2x)^2

Ptotal= P(NOCl) +P(NO)+ P(Cl2) = 1-2x+2x+x= 1+x
also Ptotal=1.135, so
1+x=1.135 => x=0.135
so
Kp= (4*0.135^3)/((1-2*0.135)^2) =0.0185