Let's analyze the
potential energy diagram provided and answer each question step by step.
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Given Diagram Summary:
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Reactants: \( X_2 + Y_2 \) at
50 kJ
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Products: \( 2XY \) at
100 kJ
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Activation Energy (forward): The peak of the curve is at
130 kJ
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Energy change: From reactants to products, energy increases from 50 kJ to 100 kJ
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Now, let’s go through each question:
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1. Is the overall reaction as shown exothermic or endothermic?
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Answer:
Endothermic
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Explanation: The products (\(2XY\)) have higher potential energy (100 kJ) than the reactants (\(X_2 + Y_2\), 50 kJ). Since energy is absorbed to form products, the reaction is
endothermic.
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2. What is the activation energy for the forward reaction?
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Answer:
80 kJ
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Explanation: Activation energy = Energy of the transition state – Energy of reactants
\( E_a = 130\ \text{kJ} - 50\ \text{kJ} = 80\ \text{kJ} \)
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3. What is the activation energy for the reverse reaction?
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Answer:
30 kJ
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Explanation: For the reverse reaction (from products to reactants), activation energy = Energy of transition state – Energy of products
\( E_a = 130\ \text{kJ} - 100\ \text{kJ} = 30\ \text{kJ} \)
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4. What is the enthalpy change of reaction (ΔH) for the forward reaction?
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Answer:
+50 kJ
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Explanation: ΔH = Energy of products – Energy of reactants
\( \Delta H = 100\ \text{kJ} - 50\ \text{kJ} = +50\ \text{kJ} \)
Positive value indicates an
endothermic reaction.
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5. What is the ΔH for the reverse reaction?
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Answer:
–50 kJ
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Explanation: Reverse reaction has opposite sign of ΔH.
So, \( \Delta H = -50\ \text{kJ} \) →
exothermic
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6. Is the reverse reaction exothermic or endothermic?
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Answer:
Exothermic
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Explanation: As shown above, ΔH = –50 kJ, meaning energy is released in the reverse direction.
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7. Which species forms the activated complex?
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Answer:
The peak of the curve (transition state)
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Explanation: The
activated complex (also called transition state) is the high-energy, unstable intermediate at the peak of the curve. It is formed when reactants collide with sufficient energy and proper orientation. In this case, it is represented by the highest point on the graph, which is
not labeled, but we know it is the
transition state between \( X_2 + Y_2 \) and \( 2XY \).
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8. Which species or set of species has the highest potential energy?
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Answer:
The activated complex (transition state)
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Explanation: The
peak of the curve represents the
activated complex, which has the
highest potential energy in the reaction pathway.
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✔ Final Answers:
1.
Endothermic
2.
80 kJ
3.
30 kJ
4.
+50 kJ
5.
–50 kJ
6.
Exothermic
7.
The activated complex (transition state)
8.
The activated complex (transition state)
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Let me know if you'd like a visual explanation or sketch!
Parent Tip: Review the logic above to help your child master the concept of potential energy diagram worksheet.
