The energy profile diagram below represents a particular reaction - VCE - SSCE Chemistry - Question 13 - 2018 - Paper 1
Question 13
The energy profile diagram below represents a particular reaction. One graph represents the uncatalysed reaction and the other graph represents the catalysed reactio... show full transcript
Worked Solution & Example Answer:The energy profile diagram below represents a particular reaction - VCE - SSCE Chemistry - Question 13 - 2018 - Paper 1
Step 1
E_a uncatalysed reaction (kJ mol⁻¹)
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Answer
The uncatalysed reaction has a higher activation energy (E_a) compared to the catalysed reaction. By analyzing the energy profile diagram, it can be inferred that the activation energy for the uncatalysed reaction is 40 kJ mol⁻¹.
Step 2
E_a catalysed reaction (kJ mol⁻¹)
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Answer
The catalysed reaction has a lower activation energy. From the diagram, we observe that the activation energy (E_a) is reduced to 0 kJ mol⁻¹, which cannot be directly seen in the options presented.
Step 3
ΔH (kJ mol⁻¹)
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Answer
The enthalpy change (ΔH) for the reaction can be estimated based on the starting and ending energies shown in the diagram. The uncatalysed reaction starts at an energy level and ends at a significantly lower one as indicated, leading to an overall ΔH of -50 kJ mol⁻¹.
Step 4
Conclusion
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Answer
Based on these observations, the correct answer that fits the energy profile in the question is: D. 40 kJ mol⁻¹ (uncatalysed) and -50 kJ mol⁻¹ for the enthalpy change.
