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Multiple Choice
Which of the following substances would have the highest boiling point?
A
CO_2
B
H_2O
C
NH_3
D
CH_4
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Verified step by step guidance
1
Step 1: Understand that boiling point depends on the strength of intermolecular forces present in the substance. Stronger intermolecular forces result in higher boiling points because more energy is required to separate the molecules from the liquid phase to the gas phase.
Step 2: Identify the types of intermolecular forces present in each substance: CO_2 is nonpolar and exhibits only London dispersion forces; CH_4 is also nonpolar with only London dispersion forces; NH_3 is polar and exhibits hydrogen bonding due to N-H bonds; H_2O is polar and exhibits strong hydrogen bonding due to O-H bonds.
Step 3: Compare the strength of hydrogen bonding in NH_3 and H_2O. Oxygen is more electronegative than nitrogen, so the O-H hydrogen bonds in water are stronger than the N-H hydrogen bonds in ammonia, leading to a higher boiling point for water.
Step 4: Recognize that CO_2 and CH_4 have only weak London dispersion forces, so their boiling points are much lower compared to substances with hydrogen bonding.
Step 5: Conclude that H_2O has the highest boiling point among the given substances because it has the strongest intermolecular forces (hydrogen bonding) compared to NH_3, CO_2, and CH_4.