This problem is providing information about the equilibrium reaction whereby nitrogen dioxide gas produced dinitrogen tetroxide gas as shown on the attached picture and the following chemical equation:
NO₂ (g) ⇄ N₂O₄ (g)
In such a way, we can consider the given choices to reason the following: the blue arrow is pointing out the arrival to the equilibrium condition for the reaction, a point in which the rate of the forward reaction (formation of N₂O₄) is equal to the rate of the reverse reaction (formation of NO₂), because the molecules will fluctuate to the same relative amounts defined by the equilibrium constant.
Therefore the answer will be the first one on the attached file, which can vary on your online homework format.
It is important to note that the reactant is not used up at any point of the graph (concentration drops to 0) and also, the activation energy cannot be analyzed with this sparse information.
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