Directions: Questions 4-7 are short free-response questions that require about 9 minutes each to answer and are worth 4 points each. Write your response in the space provided following each question. Examples and equations may be included in your responses where appropriate. For calculations, clearly show the method used and the steps involved in arriving at your answers. You must show your work to receive credit for your answer. Pay attention to significant figures. Chlorofluorocarbons are byproducts of many different processes that are known to be dangerous to the environment as both as a greenhouse gas, as well as an agent for ozone \(\left(O_{3}\right)\) depletion. The accepted mechanism for the latter is: $$\begin{array}{l}{\text { Step } 1 : \mathrm{Cl}(g)+\mathrm{O}_{3}(g) \rightarrow \operatorname{ClO}(g)+\mathrm{O}_{2}(g)} \\ {\text { Step } 2 : \mathrm{O}(g)+\operatorname{ClO}(g) \rightarrow \mathrm{Cl}(g)+\mathrm{O}_{2}(g)}\end{array}$$ (a) Write out the full reaction with the above elementary steps, and identify all catalysts and intermediates. (b) Describe two ways by which a catalyst can reduce the activation energy of a reaction. (c) Both elementary steps in the reaction above are exothermic. On the axes provided, draw a potential reaction mechanism which supports this.

Step by step solution

01

Write out the full reaction

In order to write out the full reaction with the above elementary steps, combine the two steps together by canceling intermediates. The full reaction is \[ \mathrm{Cl}(g) + \mathrm{O}(g) + \mathrm{O}_{3}(g) \rightarrow \mathrm{Cl}(g) + 2\mathrm{O}_{2}(g)\]. Here, Chlorine (Cl) acts as a catalyst because it is not consumed in the process and Chlorine monoxide (ClO) is an intermediate compound which is formed and then used up in the reaction

02

Explain how catalysts reduce activation energy

A catalyst can reduce the activation energy in a number of ways: 1. It provides an alternative pathway with lower activation energy for the reaction. This way, it becomes easier for reactants to reach the activation energy and convert into products. 2. It can interact with the reactants to form a new intermediate compound. This temporary compound requires less energy to proceed to the product state.

03

Draw a potential reaction mechanism

Regarding drawing a potential energy diagram for the reaction mechanism, unfortunately, it's not possible to draw it in the JSON format. But to guide how it should be done: Since both elementary steps in the reaction are exothermic, the potential energy of the products is less than that of the reactants in both steps. The energy diagram would show two peaks, for the transition states of the two steps, and these peaks would be higher than either the reactants or the products. The first peak would correspond to step 1 and the second to step 2. The energy level of the ClO intermediate would be in between the two peaks, and each peak would be the transition state of each step

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