Equillibrium question.?

Question

A 4.00 L flask is filled .75mol of SO3 , 2.5 mol SO2 and 1.3 mol O2, and allowed to reach equillibrium. Predict the effect on the concentrations of SO3 as equillibrium is achieved by using Q, the reaction quotient. Kc= 12
the answer is[SO3] will decrease because Q
MY question is how do you get that

Answer 1

1. write the equation: 2SO2 + O2 -----> 2SO3

2. write the Kp expression

3. work out
(0.75/4)squared/((2.5/4)squared x 1.3/4). This is Q

4. compare Q with the given value of Kc. If Q

Answer 2

ok, im assuming the equation for this reaction is 2SO3 --> 2SO2 + O2, knowing that, we know that ([O2][SO2]^2)/[SO3]^2 is Q and we know what the concentrations are by dividing the moles over liters of the flask so through substitution we get [0.325][0.625]^2/[0.1875]^2 which turns out to be a Q value of 3.61 and since the Q is lower than the equilibrium value K, we need to increase it by decreasing the concentration of the reactant SO3 as the denominator in the equilibrium constant to increase the Q value and make it eventually reach the Kc of 12 which means the equilibrium shifts to the right. By the way, Q is the reaction quotient of the initial products over reactants while K is the equilibrium value of the products over reactants which always stays constant except for when there is a change in temperature. Hope that helps...