Achieve HW Week 1 #2

[Gabi_Maldonado_1B]

Hi I keep getting the wrong answer for 2 and I think its because my ICE box set up is incorrect. Can some one talk me through how they set up the ice box for this question?:
At a certain temperature, 0.600 mol SO3 is placed in a 4.00 L container.
2SO3(g)↽−−⇀2SO2(g)+O2(g)
At equilibrium, 0.110 mol O2 is present. Calculate Kc.

[Ethan Famas 1H]

We only have SO₃ in the beginning, and based on the coefficients of the equation, SO₃ would decrease by 2x, SO₂ would increase by 2x, and O₂ would increase by x.
Be careful to put only concentration values in the ice table, which are measured in Molarity. You are given only the amount of moles, so divide the moles by the volume.
And, don't forget to raise the concentration values by their respective power which matches with their coefficient in the formula. (ex. Square the concentration for SO₃.)

[Antonia Valencia 2H]

Hi! In order to set up the ICE box for this problem, you must first start with the I section for initial concentrations The question states that there are 0.600 mols of SO3, so for now, this will be what we place as the initial concentration of SO3 (even though it is not a concentration, which would be mol.L^-1). The initial concentrations of the other two products are not given, so they would be 0. For the C section of the ICE box, the unknown changes will be dictated by the molar ratio. As. such, because the reaction is 2SO3(g)↽−−⇀2SO2(g)+O2(g), the change for SO3 would be -2X, the change for SO2 would be +2X, and the change for O2 would simply be +X. Finally, for the E section, we would simply add the initial concentration values to their corresponding changes. However, it is important to note that the question states "At equilibrium, 0.110 mol O2 is present" -- because of this, we know that in the E section of the icebox, O2 will have this value. Hence, we find out that for O2, 0 + X = 0.110, or that X = 0.110. Using this information, we can go to the other values in E section of the ICE box, and determine the number of moles for each molecule at equilibrium. Once we determine the number of moles, we have to convert these mols into molarity, which would be mol/L. Finally, in order to compute Kc, we place the determined concentrations into the Kc ratio defined by the chemical equation. Hope this helps.