QuestionApril 20, 2025

Which molecular formula has the lowest boiling point? C_(3)H_(8) C_(2)H_(6) CH_(4)

Which molecular formula has the lowest boiling point? C_(3)H_(8) C_(2)H_(6) CH_(4)
Which molecular formula has the lowest boiling point?
C_(3)H_(8)
C_(2)H_(6)
CH_(4)

Solution
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Answer

C. CH_{4} Explanation 1. Identify the Molecular Structures Methane (CH_4), Ethane (C_2H_6), and Propane (C_3H_8) are all alkanes, which are hydrocarbons with single bonds. The boiling point generally increases with molecular weight. 2. Compare Molecular Weights Calculate the molecular weights: CH_4 = 16 \, \text{g/mol}, C_2H_6 = 30 \, \text{g/mol}, C_3H_8 = 44 \, \text{g/mol}. Methane has the lowest molecular weight. 3. Relate Molecular Weight to Boiling Point Lower molecular weight typically correlates with a lower boiling point due to weaker van der Waals forces in smaller molecules. Thus, CH_4 should have the lowest boiling point.

Explanation

1. Identify the Molecular Structures<br /> Methane ($CH_4$), Ethane ($C_2H_6$), and Propane ($C_3H_8$) are all alkanes, which are hydrocarbons with single bonds. The boiling point generally increases with molecular weight.<br />2. Compare Molecular Weights<br /> Calculate the molecular weights: $CH_4 = 16 \, \text{g/mol}$, $C_2H_6 = 30 \, \text{g/mol}$, $C_3H_8 = 44 \, \text{g/mol}$. Methane has the lowest molecular weight.<br />3. Relate Molecular Weight to Boiling Point<br /> Lower molecular weight typically correlates with a lower boiling point due to weaker van der Waals forces in smaller molecules. Thus, $CH_4$ should have the lowest boiling point.
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