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Tracking Heat Through Two Reaction Paths 4 questions
Tracking Heat Through Two Reaction Paths
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A reaction model starts with the same amount of substance A and ends with the same amount of substance C at the same temperature and pressure in both trials. The direct path goes from A to C. The two-step path goes from A to B and then from B to C. Positive energy changes mean the material absorbs energy. Negative changes mean it releases energy.
| Step | Energy change of the material (kJ) |
|---|---|
| A to B | +40 |
| B to C | −70 |
| A to C in one step | −30 |
Question 1
Which listed step requires a net energy input?
- A to B
- B to C
- A to C in one step
- Every listed step
Question 2
Calculate the net energy change along the two-step path. Compare it with the direct measurement.
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Question 3
A student says the two-step path releases 70 kJ overall because that is the amount measured in the second step. Explain what the comparison leaves out.
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A repeat starts with A and carries out only the first step. Its recovered material remains B. The model also tests the reverse change from B back to A.
Question 4
Predict the net energy changes for the partial path and for its reverse. Explain why neither should be compared directly with the 30 kJ release from A to C.
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