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Choosing a Time to Stop a Model Reaction 4 questions
Choosing a Time to Stop a Model Reaction
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A class models a color-making process with a useful colored product P and a different product Q. It begins with 100 identical starting particles. Each starting particle can become one P or one Q particle. The display gives snapshots of total product counts at four stopping times.
| Time (s) | P particles | Q particles |
|---|---|---|
| 10 | 34 | 2 |
| 20 | 58 | 9 |
| 30 | 65 | 18 |
| 40 | 67 | 26 |
Question 1
During which recorded 10 s interval does P increase by the largest amount?
- 10–20 s
- 20–30 s
- 30–40 s
- The increase is the same in all three intervals.
Question 2
Calculate the number of starting-form particles that remain at 30 s, assuming the display has no other forms.
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A useful batch must have at least 55 particles of P and at most 12 particles of Q. The class can stop at one of the recorded times.
Question 3
Choose a stopping time and show how both requirements are met. Explain why waiting until P is largest would fail.
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Question 4
The class can make one more measurement between 20 s and 30 s. State both readings it should record to check whether a later stopping time gives more P while still meeting the constraints.
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