Potential Energy Diagram illustrating the energy changes during a chemical reaction, highlighting activation energy and enthalpy change.

Let’s go step by step to answer each question using the potential energy diagram.

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Step 1: Understand the diagram

- The y-axis is Potential Energy (in kJ).
- The x-axis is Progress of Reaction.
- We start with reactants: X₂ + Y₂ at about 50 kJ.
- We end with products: 2XY at about 100 kJ.
- There’s a peak in the middle — that’s the activated complex, labeled X₂Y₂, at about 150 kJ.

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Question 1: Is the overall reaction exothermic or endothermic?

→ Look at the energy of reactants vs. products.

Reactants (X₂ + Y₂) = 50 kJ
Products (2XY) = 100 kJ

Since products have more energy than reactants, energy was absorbed → endothermic

✔ Answer: Endothermic

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Question 2: What is the activation energy for the forward reaction?

→ Activation energy = energy needed to get from reactants to the activated complex.

Activated complex = 150 kJ
Reactants = 50 kJ
So, 150 - 50 = 100 kJ

✔ Answer: 100 kJ

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Question 3: What is the activation energy for the reverse reaction?

→ Reverse reaction goes from products back to reactants.

Activated complex = 150 kJ
Products = 100 kJ
So, 150 - 100 = 50 kJ

✔ Answer: 50 kJ

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Question 4: What is the enthalpy change (ΔH) for the forward reaction?

→ ΔH = energy of products – energy of reactants

= 100 kJ – 50 kJ = +50 kJ

(Positive means endothermic)

✔ Answer: +50 kJ

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Question 5: What is the ΔH for the reverse reaction?

→ Reverse reaction: products become reactants.

ΔH_reverse = energy of reactants – energy of products
= 50 kJ – 100 kJ = –50 kJ

(Negative means exothermic)

✔ Answer: –50 kJ

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Question 6: Is the reverse reaction exothermic or endothermic?

→ From Q5, ΔH = –50 kJ → negative → releases heat → exothermic

✔ Answer: Exothermic

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Question 7: Which species form the activated complex?

→ The peak is labeled X₂Y₂

✔ Answer: X₂Y₂

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Question 8: Which species or set of species has the highest potential energy?

→ Look at the diagram:

- X₂ + Y₂ = 50 kJ
- 2XY = 100 kJ
- X₂Y₂ (activated complex) = 150 kJ ← highest!

✔ Answer: X₂Y₂

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Final Answer:
1. Endothermic
2. 100 kJ
3. 50 kJ
4. +50 kJ
5. –50 kJ
6. Exothermic
7. X₂Y₂
8. X₂Y₂