Question

Dinitrogen tetroxide decomposes to produce nitrogen dioxide gas. When dinitrogen tetroxide is sealed in an evacuated glass container, the closed system eventually reaches dynamic equilibrium. Which statement describes the graph of the rate of the forward reaction over time? It starts high and gradually decreases until it levels out above zero. It starts high and gradually decreases until it reaches a rate of zero. It starts low and gradually increases until it levels out at a rate above zero. It starts low and gradually increases until it reaches a maximum rate.

Answer 1

The formula for Dinitrogen tetroxide is N₂O₄ while that of Nitrogen Dioxide is NO₂. The balance reaction is

N₂O₄ ⇄ 2 NO₂

The reaction is actually an equilibrium reaction, but the forward reaction is the spontaneous one. In this decompostion reaction, the reactant is N₂O₄. At the start of the reaction, there is an abundant amount of reactant and zero moles of product. As time goes by, the reactant is slowly converted to NO₂. So, you would expect that at the start the forward reaction has a very fast rate. As time goes by, the amount of reactant will deplete so the rate slowly decreases until it levels to zero. If you graph it in a qualitative curve, it would look like that in the picture.

The answer is: It starts high and gradually decreases until it reaches a rate of zero.