Question

What happens to the following reaction at equilibrium if the pressure is decreased?
2H"subtext"2(g) + O"subtext"2(g) 2H"subtext"2O(g)

Answer 1

You could save a lot of time by using this:
2H2 + O2 ==> 2H2O. Everyone knows that the number two following H and O are subscripts. We CAN write them as subscripts but no one wants to take the time to do it.
2H₂ + O₂ ===> 2H₂O

Here is the rule to follow:
An increase in pressure for a gaseous system in equilibrium causes the equilibrium to shift in the direction of FEWER moles. Decrease in P does the opposite.

Answer 2

so it shifts to the right because Q < K correct?

Answer 3

I don't think so.
H2 + O2 ==> 2H2O

If P increases, it shifts to side with fewer moles of gases. There are 3 mols on the left; two moles on the right so for increase P it shifts to the right. A decrease in P must shift to the left.