Determining pressure at equilibrium with Kp

[Emworthington]

Homework Statement

The minerals (Fe2So3) and (Fe3O4) exist in equilibrium with atmospheric oxygen.

4 Fe3O4(s) + O2(g) <----> 6 Fe2O3(s) kp = 2.5 x 10^87

Determine P(O2) at equilibrium

Homework Equations

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The Attempt at a Solution

Since the equilibrium constant can only have gases in it, I assumed that the equation would be
1/[O2]^2 so that the pressure would be 1/2.5*10^87. However, it's an online program and says that that (4*10^-88) is wrong. It also says that 2.5*10^87 is wrong. What else do you think I could do?

 

[Borek]

No idea why 1/[O₂]² and not just 1/[O₂], but perhaps that's just a typo.

Some of these HW programs are very anal about significant digits.