Question 19
The reaction
A + B → C; ΔH negative
involves a two-step process
A + B → X; ΔH positive
X → C; ΔH negative
Which one of the following diagrams best represents the energy changes during the course of the reaction?
A - VCE - SSCE Chemistry - Question 19 - 2007 - Paper 1
Question 19
Question 19
The reaction
A + B → C; ΔH negative
involves a two-step process
A + B → X; ΔH positive
X → C; ΔH negative
Which one of the following diagrams... show full transcript
Worked Solution & Example Answer:Question 19
The reaction
A + B → C; ΔH negative
involves a two-step process
A + B → X; ΔH positive
X → C; ΔH negative
Which one of the following diagrams best represents the energy changes during the course of the reaction?
A - VCE - SSCE Chemistry - Question 19 - 2007 - Paper 1
Step 1
A + B → C; ΔH negative
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Answer
This part of the reaction indicates that the overall process is exothermic, where energy is released, leading to a decrease in energy as the reaction progresses from reactants to products.
Step 2
A + B → X; ΔH positive
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Answer
This intermediate step is endothermic, suggesting that energy is absorbed to form the intermediate X. Therefore, the energy of the system increases at this step.
Step 3
X → C; ΔH negative
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Answer
The second step is again exothermic, meaning energy is released as X converts to C, resulting in a decrease in energy as the final product is formed.
Step 4
Choose the correct diagram
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Answer
Based on these energy changes, the diagram that correctly represents this sequence will show an initial rise in energy when A + B turns into X, followed by a drop in energy when X converts to C. Hence, the correct answer is option D.
