3.1 Define the term vapour pressure - NSC Physical Sciences - Question 3 - 2021 - Paper 2
Question 3
3.1 Define the term vapour pressure.
3.2 Write down the independent variable for this investigation.
3.3 Which compound, A or B, has the higher vapour pressure?
3... show full transcript
Worked Solution & Example Answer:3.1 Define the term vapour pressure - NSC Physical Sciences - Question 3 - 2021 - Paper 2
Step 1
Define the term vapour pressure.
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Answer
Vapour pressure is defined as the pressure exerted by a vapour in equilibrium with its liquid in a closed system.
Step 2
Write down the independent variable for this investigation.
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Answer
The independent variable for this investigation is temperature.
Step 3
Which compound, A or B, has the higher vapour pressure?
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Answer
Compound B, butan-2-one, has the higher vapour pressure.
Step 4
Fully explain the answer to QUESTION 3.3. Include the TYPES OF INTERMOLECULAR FORCES in your explanation.
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Answer
Butan-1-ol exhibits hydrogen bonding due to the presence of an -OH group, while butan-2-one has dipole-dipole interactions and London dispersion forces. Hydrogen bonds are generally stronger than dipole-dipole forces. Therefore, the weaker intermolecular forces in butan-2-one allow it to have a higher vapour pressure compared to butan-1-ol.
Step 5
Write down the term for the temperature represented by X.
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Answer
Boiling point (of compound A, butan-1-ol).
Step 6
State the phase of compound A at temperature Y. Choose from GAS, LIQUID or SOLID.
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Answer
Gas.
Step 7
Redraw the graph above in your ANSWER BOOK. On the same set of axes, sketch the curve that would be obtained for compound C. Clearly label curve A and curve C.
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Answer
For the graph, ensure that curve A starts at point (101.3, X) and follows an upward trend to Y. Curve C should start lower on the Y-axis and have a less steep incline, indicating lower vapour pressure across the temperature range.
