At 25°C, Kp 1 10-31 for the following reaction:

Question

N2(g) + O2(g) 2 NO(g)

Calculate the concentration of NO, in molecules/cm3, that can exist in equilibrium in air at 25°C. In air, PN2 = 0.8 atm and PO2 = 0.2 atm.

Answer 1

You need to identify the equal sign on your keyboard (and use it)
Is Kp = 1E-31?
The arrow can be made as ==> or -->. Use that too.
Kp = PNO^2/PN2*PO2
Solve for PNO2.
That 0.8 and 0.2 are 80% and 20% by volume. That means 80 L N2/100L air, 20 L O2/100 L air and %NO = your number x (100/100) = ?
Convert that to moles (divide by 22.4 L/mol) and multiply by 6.02E23 to obtain # molecules/L, then convert to cc. Check my thinking. 1 mole air will occupy 24.5 L at STP instead of 22.4 so you may want to use that number instead of 22.4.