Overall reaction and enthalpy diagram for NO₂ mechanism

[scrimmage]

chemistry help!

hi, i really really really need help with this question, i missed 2 days of class, now i don't know what's goin on, I am completely lost, and i have a test 2morow on this topic, and a friend told me the teacher said a question of this type will be on this test. i have went through my test book and learned all the other stuff but this is all that i absolutly don't get! , i just went blank. if someone ANYONE with knowledge if this can help me, i'd really appreciate it, i wouldent do this unless i was desprate , i feel like a retard but here it goes...


Consider The following reaction mechanism

2NO(subscript2) (g) -----> NO(subscript3) (g) + NO(g) Ea(activation energy = + 100 KJ delta(triangle)H = + 50KJ

NO(subscript3) (g) + CO (g) --------> NO(subscript2) (g) + CO(subscript2) Ea = 200KJ deltaH = - 150 KJ

a) write the overall reaction(rxn) for the above mechanism, and calculate the overall enthalpy change and activation energy.

b) draw a fully labelled enthalpy diagram include labelled axes, enthalpy changes, Ea, activated complex, productts reactants and illistrate how a catalyst would affect the rxn (reaction).

thanks a lot for anyone that can help or explain this to me, i got to know how to do this for 2morow

 

[M98Ranger]

Hi there,

I can understand how stressful it can be to have an exam tomorrow and feeling lost in a subject. Chemistry can be tricky at times, but with some practice and understanding, you can definitely get through this. I'll try my best to explain the problem and provide some tips for you to prepare for your exam.

Firstly, let's break down the problem into smaller parts. The given reaction mechanism involves two reactions, one is the formation of NO3 and NO from NO2, and the second one is the reaction between NO3 and CO to form NO2 and CO2. In order to write the overall reaction, we need to cancel out the common reactants and products. In this case, NO3 and NO are common in both reactions, so they will cancel out. This leaves us with the overall reaction as:

2CO (g) -----> 2CO2 (g)

Now, for calculating the overall enthalpy change, we need to add the enthalpy changes for each step in the reaction mechanism. The first reaction has a deltaH of +50 KJ and the second reaction has a deltaH of -150 KJ. When we add these, we get a net deltaH of -100 KJ. This means that the overall reaction is exothermic.

For calculating the activation energy, you need to look at the highest energy barrier in the reaction mechanism. In this case, it is the second step with an Ea of 200 KJ. So, the overall activation energy for the reaction is 200 KJ.

For drawing the enthalpy diagram, you can start by labeling the axes - x-axis as reaction progress and y-axis as enthalpy. Then, plot the enthalpy changes for each step in the reaction mechanism. For the first step, you will have a +50 KJ change, so the line will go up. For the second step, you will have a -150 KJ change, so the line will go down. The difference between the highest and lowest points on the graph will give you the overall enthalpy change. To show the effect of a catalyst, you can draw a dotted line with a lower activation energy, indicating that the presence of a catalyst lowers the energy barrier for the reaction.

I hope this helps you understand the problem better. It's important to practice similar problems and go through your notes and textbook to get a better understanding of the topic. Also, make sure