Question

Ammonia and oxygen react to form nitrogen monoxide and water, like this:
4NH3
(g)
+
5O2
(g)
→
4NO
(g)
+
6H2O
(g)
Write the pressure equilibrium constant expression for this reaction.

Answer 1

4NH3+5O2 <=>4NO + 6H2O

Using the definition of Kp, we have
Kp=(Pno^4*Ph2o^6)/(Pnh3^4*Po2^5)
where Pno=partial pressure of NO, etc.

The numerical value for a given temperature can be evaluated when the actual partial pressures are known.