Question:
Which among the following has lowest boiling point?
Which among the following has lowest boiling point?
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Boiling point $\propto$ Molar Mass (for similar functional groups).
Updated On: Apr 30, 2026
- Pentanal
- Propanal
- Methanal
- Ethanal
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The Correct Option is C
Solution and Explanation
Step 1: Factor affecting Boiling Point
For a homologous series of aldehydes, boiling point increases with an increase in molar mass and surface area (van der Waals forces).
Step 2: Comparison of Molar Mass
- Methanal ($HCHO$): 30 g/mol - Ethanal ($CH_3CHO$): 44 g/mol - Propanal ($C_2H_5CHO$): 58 g/mol - Pentanal ($C_4H_9CHO$): 86 g/mol
Step 3: Conclusion
Methanal (Formaldehyde) is the simplest member with the lowest molar mass and thus the lowest boiling point (it is a gas at room temperature).
Final Answer:(C)
For a homologous series of aldehydes, boiling point increases with an increase in molar mass and surface area (van der Waals forces).
Step 2: Comparison of Molar Mass
- Methanal ($HCHO$): 30 g/mol - Ethanal ($CH_3CHO$): 44 g/mol - Propanal ($C_2H_5CHO$): 58 g/mol - Pentanal ($C_4H_9CHO$): 86 g/mol
Step 3: Conclusion
Methanal (Formaldehyde) is the simplest member with the lowest molar mass and thus the lowest boiling point (it is a gas at room temperature).
Final Answer:(C)
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