#14 chem. equilibrium part 4 post-module assessment

[Hailey Boehm 2H]

Question #14 on the chemical equilibrium part 4 post-module assessment states the following:
14. The two air pollutants SO2 and NO2 can react in the atmosphere as follows:
SO2 (g) + NO2 (g) ⇌ SO3 (g) + NO (g)
Predict the effect of the following changes to the amount of NO when the reaction above has come to equilibrium in a stainless steel bulb equipped with entrants for chemicals.
i. The amount of NO2 is increased.
ii. The SO3 is removed by condensation.
iii. The pressure is tripled by pumping in helium.

A. i = Increase in NO, ii = No effect on NO, iii = No effect on NO

B. i = Increase in NO, ii = Increase in NO, iii = Increase in NO

C. i = Increase in NO, ii = Increase in NO, iii = No effect on NO

D. i = No effect on NO, ii = Increase in NO, iii = No effect on NO

I thought the answer was B, but this answer is wrong. I understand that part i is increase in NO because more reactant is added so the reaction shifts to the right, but I am unsure on part ii and iii. Can somebody explain what the right answer is and why? Thanks!

[Kate_Santoso_4F]

The correct answer should be C. If the amount of NO2 is increased, the equlibrium will shift to the products, which will result in an increase in NO. If SO3 is removed by condensation, the equilibrium will shift to the products again, which will result in an increase in NO. If the pressure is tripled by pumping in helium, there will be no effect on NO because helium is an inert gas and increasing the pressure by introducing an inert gas has no effect on the equilibrium composition.

[Nicole Elhosni 2I]

Helium is an inert gas so it will have no effect on the reaction. But if it was a gas that did have an effect, in the case of this reaction, it would not lean right or left since the moles of gases are the same for the reactants and products.