Worksheet 1-2: Potential Energy Diagrams for chemistry students.

Since I can't view or access uploaded images directly, I can’t see the specific potential energy diagram you’re referring to. However, based on your description and the typical structure of a potential energy diagram for a chemical reaction (like the one in your worksheet), I can help you solve the problems step-by-step.

Let’s assume the diagram shows:

- A reaction coordinate (progress of reaction) on the x-axis.
- Potential energy on the y-axis.
- Two species: reactants (X₂ + Y₂) and products (2XY).
- An energy barrier (activation energy) between them.
- A peak representing the transition state (activated complex).
- The reaction is exothermic, since the products are at lower energy than the reactants.

Here's how we typically interpret such diagrams and answer the questions:

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Given Diagram Assumptions:

- Reactants: X₂ + Y₂ → 2XY
- Energy of reactants = 150 kJ/mol
- Energy of products = 70 kJ/mol
- Peak (transition state) = 300 kJ/mol

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Now let's solve each question:

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#### 1. Is the overall reaction exothermic or endothermic?

✔ Answer: Exothermic
Explanation: The products have lower potential energy than the reactants (70 < 150). Energy is released during the reaction. In exothermic reactions, ΔH is negative.

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#### 2. What is the activation energy for the forward reaction?

✔ Answer: 150 kJ/mol
Explanation: Activation energy (Eₐ) is the energy difference between the reactants and the transition state.

> Eₐ(forward) = Energy of transition state – Energy of reactants
> = 300 kJ/mol – 150 kJ/mol = 150 kJ/mol

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#### 3. What is the activation energy for the reverse reaction?

✔ Answer: 230 kJ/mol
Explanation: For the reverse reaction (2XY → X₂ + Y₂), the activation energy is the difference between the products and the transition state.

> Eₐ(reverse) = Energy of transition state – Energy of products
> = 300 kJ/mol – 70 kJ/mol = 230 kJ/mol

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#### 4. What is the enthalpy change of reaction (ΔH) for the forward reaction?

✔ Answer: –80 kJ/mol
Explanation: ΔH = Energy of products – Energy of reactants
= 70 kJ/mol – 150 kJ/mol = –80 kJ/mol

Negative sign indicates exothermic.

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#### 5. What is ΔH for the reverse reaction?

✔ Answer: +80 kJ/mol
Explanation: The reverse reaction has the opposite sign of ΔH.
ΔH(reverse) = –(ΔH(forward)) = +80 kJ/mol

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#### 6. Is the reverse reaction exothermic or endothermic?

✔ Answer: Endothermic
Explanation: Since ΔH is positive (+80 kJ/mol), the reverse reaction absorbs heat.

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#### 7. Which species forms the activated complex?

✔ Answer: The transition state (at the peak)
Explanation: The activated complex (or transition state) is the high-energy intermediate formed at the top of the energy barrier. It is not a stable molecule but a fleeting arrangement of atoms with partial bonds.

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#### 8. Which species or set of atoms has higher potential energy?

✔ Answer: The activated complex (transition state)
Explanation: The transition state has the highest potential energy on the diagram. It is the unstable, high-energy configuration that must be overcome for the reaction to proceed.

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✔ Summary Table:

| Question | Answer |
|--------|--------|
| 1. Overall reaction type | Exothermic |
| 2. Eₐ (forward) | 150 kJ/mol |
| 3. Eₐ (reverse) | 230 kJ/mol |
| 4. ΔH (forward) | –80 kJ/mol |
| 5. ΔH (reverse) | +80 kJ/mol |
| 6. Reverse reaction type | Endothermic |
| 7. Activated complex | Transition state (peak) |
| 8. Highest potential energy | Transition state |

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If your diagram has different values (e.g., different energy levels), please provide those numbers, and I can adjust the answers accordingly.

Let me know if you'd like this explained with a sketch or labeled diagram!