finding the pressure at equilibrium

Question

Consider the following reaction.

If a sample of A(g) at 2.60 atm is heated to 500 K, what is the pressure of B(g) at equilibrium?

2A(g)--><--B(g) kp=4.22x10^-5 at 500 k

Answer 1

2A(g) <===> B(g) ... Kp = 4.22x10^-5

2.60............0.......Initial.....

-2x...........+x.........Change....

2.60-2x......x........Equilibrium....

Kp = 4.22x10^-5 = P_B/(P_A)² = x/(2.60-x)²

4.22x10^{-5 =}x/x² -5.2x + 6.76

Using the quadratic equation, solve for x and that will be the pressure of B at equilibrium.