Question

Consider the reaction:
SO2 (g) + NO2 (g) ==> SO3 (g) + NO (g)
At T = 1000 K, where the reaction is exothermic with an equilibrium constant K = 9.00

The reaction vessel is charged initially with all four gases, each at a pressure of 0.5 atm. After equilibrium is achieved, the partial pressure of SO3 will be:
a) 0.250 atm
b) 0.500 atm
c) 0.750 atm
d) 0.900 atm
e) none of these

Answer 1

First you must determine which way the reaction will shift to reach equilibrium.
Q = (SO3)(NO)/(NO2)(SO2) = (0.5*0.5/0.5*0.5) = 1. With K = 9 that means products are too small and reactants too large so the rxn must shift to the right to reach equilibrium.
.....SO2(g) + NO2(g) ==> SO3(g) + NO(g)
I...0.5.......0.5.........0.5.....0.5
C.....-x......-x..........x.......x
E...0.5-x...0.5-x........0.5+x...0.5+x

Substitute into Keq an solve for x, then evaluate each constituent.