A proposed mechanism for the reaction of NO2 and CO is Step 1: Slow, endothermic:
2 NO2 (g) → NO (g) + NO3 (g)

Step 2: Fast, exothermic:
NO3 (g) + CO (g) → NO2 (g) + CO2 (g)

Overall reaction, exothermic:

NO2 (g) + CO (g) → NO (g) + CO2 (g)

a. Identify each of the following as a reactant, product, or intermediate:
1. NO2(g)
2. CO(g)
3. NO3(g)
4. CO2(g)
5. NO(g)

b. Draw a reaction coordinate diagram for this reaction. Indicate on this drawing the activation energy for each step and the overall enthalpy change.

a.

1. NO2(g): Reactant.

2. CO(g): Reactant.

3. NO3(g): Intermediate.

4. CO2(g): Product.

5. NO(g): Product.

b. See attached picture.

Explanation:

Hello,

a. In this case, given the reactions, we can identify each species as:

1. NO2(g): Reactant because it remains at the left side in the overall reaction.

2. CO(g): Reactant because it remains at the left side in the overall reaction.

3. NO3(g): Intermediate because it is a product in the step 1 and a reactant in step 2, for that reason it is not present in the overall reaction.

4. CO2(g): Product because it remains at the right side in the overall reaction.

5. NO(g): Product because it remains at the right side in the overall reaction.

b. In this case, given that the first step is slow and endothermic, it has a high activation energy and the products will have more energy than the reactants, for that reason the final energy is above the initial point. Moreover, since the second step is fast and exothermic, it has a low activation energy and the products will have less energy than the reactants, for that reason, the reaction coordinate diagram is shown on the attached file.

Regards.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).