A proposed mechanism for a reaction is:
(i) A + B2 AB2 Ea1 = 12 kJ/mol ƒ´H1 = 3 kJ/mol
(ii) AB2 + C2 ABC + BC Ea2 = 30 kJ/mol ƒ´H2 = 5.2 kJ/mol
(iii) ABC + B2 AB2 + BC Ea3 = 10 kJ/mol ƒ´H3 = -7.8
kJ/mol
a) Which is the rate determining step? Explain why.
(ii) is the rate determining step because it requires the greatest increase in energy, and thus, it is the slowest step.
b) What is the overall equation for this reaction?
A + 2B2 + c2 = AB2 + 2BC delta h= 0.4 kj/mol
c) Name a reaction intermediate (1 mark)
ABC
d) Draw a completely labeled energy diagram to scale for the overall reaction. Clearly show ƒ´Hr
and Ea
?????
HELP AND PLEASE CHECK MY WORK
Your answers for parts a) and b) are correct.
For part c), the reaction intermediate is indeed ABC.
For part d), I cannot draw a diagram as I am a text-based AI bot. However, I can guide you on how to draw it yourself.
To draw the energy diagram, you need to plot the energy on the y-axis and the progress of the reaction on the x-axis.
1. Start by drawing a horizontal line to represent the energy of the reactants. Label it as A + 2B2 + C2.
2. From the reactants' level, draw a line going up to represent the activation energy for the first step (Ea1). Label it as Ea1 and indicate the value of 12 kJ/mol.
3. At the top of this line, draw a horizontal line to represent the energy of the transition state. Label it as AB2.
4. From the transition state level, draw a line going down to represent the energy change (ƒ´H1) of the first step. Label it as ƒ´H1 and indicate the value of 3 kJ/mol.
5. At the bottom of this line, draw a horizontal line to represent the energy of the intermediate (ABC).
6. From the intermediate level, draw a line going up to represent the activation energy for the second step (Ea2). Label it as Ea2 and indicate the value of 30 kJ/mol.
7. At the top of this line, draw a horizontal line to represent the energy of the transition state. Label it as ABC.
8. From the transition state level, draw a line going down to represent the energy change (ƒ´H2) of the second step. Label it as ƒ´H2 and indicate the value of 5.2 kJ/mol.
9. At the bottom of this line, draw a horizontal line to represent the energy of the products. Label it as AB2 + 2BC.
10. From the products' level, draw a line going up to represent the activation energy for the third step (Ea3). Label it as Ea3 and indicate the value of 10 kJ/mol.
11. At the top of this line, draw a horizontal line to represent the energy of the transition state. Label it as AB2 + BC.
12. From the transition state level, draw a line going down to represent the energy change (ƒ´H3) of the third step. Label it as ƒ´H3 and indicate the value of -7.8 kJ/mol.
13. At the bottom of this line, draw a horizontal line to represent the energy of the products. Label it as A + 2B2 + C2.
Make sure to scale the y-axis (energy) and x-axis (progress) appropriately to accurately represent the energy changes and activation energies.
a) To determine the rate determining step, we need to compare the activation energies (Ea) of each step. The rate determining step is the one with the highest activation energy, as it represents the slowest step in the reaction. In this case, the activation energy for step (ii) is 30 kJ/mol, which is higher than the activation energies for steps (i) and (iii). Therefore, step (ii) is the rate determining step.
b) To find the overall equation, we need to cancel out any intermediates that appear on both sides of the equations. From the given mechanisms, we can see that AB2 is an intermediate in steps (i) and (iii), and ABC is an intermediate in steps (ii) and (iii). By cancelling out AB2 and ABC, we can construct the overall equation:
A + 2B2 + C2 → AB2 + 2BC
Note that the overall equation has a delta H of 0.4 kJ/mol, but since the enthalpies of formation for the reactants and products are not provided, we cannot determine the individual enthalpies of the compounds involved.
c) An intermediate is a species that is formed during the reaction but is consumed later, without appearing in the overall balanced equation. From the given mechanisms, we can see that ABC is an intermediate, as it is formed in step (ii) and consumed in step (iii).
d) Drawing the energy diagram requires labeling the energy on the y-axis and the reaction progress on the x-axis. The reactants should be on the left and the products on the right. Each step should be represented as a separate line, with the activation energy (Ea) indicated by a dashed line and the enthalpy change (ƒ´H) indicated by an arrow. Unfortunately, as a text-based AI, I am unable to create diagrams. However, you can sketch a rough energy diagram using the provided data and labels as a guide. Remember to clearly show the delta H (ƒ´H) and Ea values for each step.