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Tracking Two Vapors Over One Liquid 4 questions
Tracking Two Vapors Over One Liquid
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A sealed display holds a mixture of liquids P and Q with their vapor above it. At this temperature the model gives each substance a vapor-pressure contribution equal to its measured fraction among liquid particles multiplied by the vapor pressure it would have as a pure liquid. The total vapor pressure is the sum of the two contributions.
| Substance | Pure-liquid vapor pressure (kPa) | Measured fraction in the first liquid |
|---|---|---|
| P | 12 | 0.50 |
| Q | 4 | 0.50 |
Question 1
Calculate the separate pressure contributions and the total vapor pressure above the starting mixture.
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In this model the fraction of vapor particles of a given substance equals its pressure contribution divided by the total vapor pressure.
Question 2
What fraction of the vapor particles above the starting liquid are P particles?
- 1/4
- 1/2
- 2/3
- 3/4
Question 3
Explain why the starting liquid and the vapor do not contain the same fraction of P particles.
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A second test uses a liquid that is one quarter P and three quarters Q at the same temperature.
Question 4
A student says equal fractions in the vapor require equal fractions in the liquid. Use the second test to evaluate the claim.
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