The reversible reaction 2SO2(g) + O2(g) 2SO3(g) has come to equilibrium in a vessel of specific volume at a given temperature. Before the reaction began, the concentrations of the reactants were 0.060 mol/L of SO2 and 0.050 mol/L of O2. After equilibrium is reached, the concentration of SO3 is 0.040 mol/L. What is the value of Kc? a) 2.7 b) 1.3 × 102 c) 7.5 × 10-3 d) 0.38 e) 40. answer is B Can anyone show my step by step how to get this? I did: [.040]²/[.060]²[.050]=8.88 Obviously I'm way off. Can anyone shed some light?? Please and thank you! :D

Question

The reversible reaction 2SO2(g) + O2(g)<===> 2SO3(g)
has come to equilibrium in a vessel of specific volume at a given temperature. Before the reaction began, the concentrations of the reactants were 0.060 mol/L of SO2 and 0.050 mol/L of O2. After equilibrium is reached, the concentration of SO3 is 0.040 mol/L. What is the value of Kc?
a) 2.7 b) 1.3 × 102 c) 7.5 × 10-3 d) 0.38 e) 40.

answer is B
Can anyone show my step by step how to get this? 
I did: [.040]²/[.060]²[.050]=8.88
Obviously I'm way off. Can anyone shed some light?? Please and thank you! :D

aaronq · Answer

0.060 mol/L of SO2 and 0.050 mol/L of O2

these values are initial values, you have to find what these are at equilibrium. Then you can plug them into the Kc expression.