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) It requires the greatest increase in energy, and thus, is the slowest.
b) What is the overall equation for this reaction?
A + 2B2 + C2 = AB2 +2BC deltaH= 0.4 kj/mol
c) Name a reaction intermediate.
ABC
d) Draw a completely labeled energy diagram to scale for the overall reaction. Clearly show deltaHr
and Ea.
?????
Please help!! Please check my work and help with d)
To answer question d), we would need to draw an energy diagram for the overall reaction using the information given in the proposed mechanism.
Let's start by labeling the energy diagram. We will have the energy on the y-axis and the progress of the reaction on the x-axis.
1. Draw the reactants on the left side of the diagram and the products on the right side, with the energy increasing from left to right.
A + 2B2 + C2 --> AB2 + 2BC
2. Label the energy of the reactants as the starting point (initial energy level) and the energy of the products as the endpoint (final energy level).
Label the initial energy as Ereactants and the final energy as Eproducts.
3. Draw an uphill curve representing the activation energy (Ea) for each step of the reaction.
- From reactants to AB2: Ea1 = 12 kJ/mol
- From AB2 to ABC + BC: Ea2 = 30 kJ/mol
- From ABC + B2 to AB2 + BC: Ea3 = 10 kJ/mol
4. Label the overall change in enthalpy (ΔHr) on the diagram.
ΔHr = 0.4 kJ/mol
You can indicate this as a vertical line or an arrow indicating the difference in energy between the reactants and products.
Remember to scale the diagram appropriately, where the vertical distance represents the energy change.
Note: Since I am a text-based AI, I am unable to draw a diagram. However, I hope these instructions help you in drawing the labeled energy diagram for the overall reaction.
To draw a completely labeled energy diagram for the overall reaction, we need to understand the individual steps of the reaction and their respective energies (Ea) and enthalpies (∆H).
Let's start by representing the reactants, intermediates, and products on the energy diagram. We have:
Reactants: A + 2B2 + C2
Intermediates: AB2, ABC
Products: AB2 + 2BC
Now, let's plot the energy axis on the diagram, with the initial energy (Ea1 = 12 kJ/mol) of the first step (i) and the ∆H1 = 3 kJ/mol at the end of step (i). We'll keep the energy constant until step (ii).
Reactants: A + 2B2 + C2
| | |
_______ |________|________|
Ea1 = 12 kJ/mol ∆H1 = 3 kJ/mol
Next, we'll plot the energy axis for the second step (ii). The Ea2 = 30 kJ/mol should be higher than the Ea1. At the end of step (ii), ∆H2 = 5.2 kJ/mol.
____________________
| | | |
____|___________|________ |
Ea1 = 12 kJ/mol Ea2 = 30 kJ/mol ∆H1 = 3 kJ/mol ∆H2 = 5.2 kJ/mol
Finally, let's include the energy axis for the third step (iii). Ea3 = 10 kJ/mol should be lower than both Ea1 and Ea2. At the end of step (iii), ∆H3 = -7.8 kJ/mol.
____________________
| | |
____|___________ | |
Ea1 = 12 kJ/mol Ea2 = 30 kJ/mol Ea3 = 10 kJ/mol ∆H1 = 3 kJ/mol ∆H2 = 5.2 kJ/mol ∆H3 = -7.8 kJ/mol
The overall ∆H of the reaction is given as 0.4 kJ/mol. We can label it as ∆Hr.
Therefore, the completely labeled energy diagram to scale for the overall reaction looks like this:
Reactants: A + 2B2 + C2
| | |
_______ |________|________|
Ea1 = 12 kJ/mol ∆H1 = 3 kJ/mol
____________________
| | | |
____|___________|________ |
Ea1 = 12 kJ/mol Ea2 = 30 kJ/mol ∆H1 = 3 kJ/mol ∆H2 = 5.2 kJ/mol
____________________
| | |
____|___________ | |
Ea1 = 12 kJ/mol Ea2 = 30 kJ/mol Ea3 = 10 kJ/mol ∆H1 = 3 kJ/mol ∆H2 = 5.2 kJ/mol ∆H3 = -7.8 kJ/mol
∆Hr = 0.4 kJ/mol
Note that the diagram is not drawn to scale since the values of Ea and ∆H are not proportional on the y-axis.