A scientist is adding oxygen to iron in a chemical reaction to create rust. Once it reaches equilibrium, this reaction will the oxygen and iron quit making rust
Option D is correct
Once the oxygen runs out is incorrect because even if the oxygen runs out, the iron atoms will continue to react with the remaining oxygen molecules until they are all used up.
In chemical equilibrium, the rate of the forward reaction (rust formation) equals the rate of the backward reaction (rust breakdown). So, even though there might be some oxygen and iron left unreacted, the overall amount of rust won't change significantly, making the production essentially stop. We also take note that factors, like the presence of impurities or a catalyst, could also influence the reaction rate and equilibrium point, but in the absence of such information, equilibrium remains the most likely explanation.