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Accounting for Gas in a Two-Solid Model 4 questions
Accounting for Gas in a Two-Solid Model
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A conservation display models two solids that release gas. Every formula unit of solid P that reacts produces one gas molecule. Every formula unit of solid Q that reacts produces two gas molecules. The display starts with 30 formula units of solid altogether. Both solids react completely.
| Run | Total starting formula units | Gas molecules counted |
|---|---|---|
| P only | 30 | 30 |
| Q only | 30 | 60 |
| Mixture | 30 | 42 |
Question 1
Which statement must be true of the mixture in this model?
- It contains only P.
- It contains only Q.
- It contains some of each solid.
- It contains equal amounts of P and Q.
Question 2
Calculate the number of P and Q formula units in the mixture. Show how the two measurements are used.
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A repeat uses the same number of units of each solid but interrupts the model before all units react. The display shows 37 gas molecules.
Question 3
Explain why the 5 missing gas molecules do not by themselves identify how many formula units failed to react.
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Question 4
Give one possible combination of unreacted P and Q that accounts for the result, and show its missing gas count.
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