The reaction between sulfur dioxide and oxygen is reversible. 2SO2(g) + O2(g) = 2SO3(g) Kc=280mol^-1 dm^3 at 1000K In an equilibrium mixture at 1000K the sulfur trioxide concentration is 6.00 mol dm^-3. What is the sulfur dioxide concentration? A) 0.175 mol dm^-3 B) 0.254 mol dm^-3 C) 0.318 mol dm^-3 D) 0.636 mol dm^-3