Chapter 12: Problem 15

Which member of each of these pairs of substances would you expect to have a higher boiling point: (a) \(\mathrm{O}_{2}\) or \(\mathrm{N}_{2},\) (b) \(\mathrm{SO}_{2}\) or \(\mathrm{CO}_{2},\) (c) HF or HI?

Short Answer

Expert verified

The substances with a higher boiling point are O2, SO2, and HF.

Step by step solution

Understanding the Concept

The boiling point of a substance depends on the strength of the intermolecular forces. The stronger the forces, the higher the boiling point. There are three types of intermolecular forces - Van der Waals forces (present in all molecules), dipole-dipole forces (present in polar molecules), and hydrogen bonds (present in molecules where hydrogen is bonded to Nitrogen, Oxygen or Fluorine). The size of the molecule and its shape can also impact these forces and hence the boiling point.

Exercise Part (a) O2 or N2

Both O2 and N2 are diatomic molecules with similar size and shape, and both are nonpolar. Therefore, the type of intermolecular force is Van der Waals forces for both. But N2 is lighter than O2, making its intermolecular forces weaker. Thus, the substance with a higher boiling point is O2.

Exercise Part (b) SO2 or CO2

Both SO2 and CO2 are triatomic molecules. CO2 is nonpolar while SO2 is a polar molecule. Thus, the type of intermolecular force is Van der Waals forces for CO2 and both Van der Waals and dipole-dipole for SO2. Though SO2 and CO2 have similar molar masses, the extra dipole-dipole interaction in SO2 makes its intermolecular forces stronger. Hence, the substance with a higher boiling point is SO2.

Exercise Part (c) HF or HI

Both HF and HI are diatomic molecules. HF can form a hydrogen bond while HI cannot. Therefore, the type of intermolecular force is hydrogen bond along with Van der Waals forces for HF and only Van der Waals forces for HI. Despite HI being significantly larger in size (and therefore having a stronger Van der Waals forces), the presence of hydrogen bonding in HF makes its intermolecular forces stronger. Hence, the substance with a higher boiling point is HF

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Which member of each of these pairs of substances would you expect to have a higher boiling point: (a) \(\mathrm{O}_{2}\) or \(\mathrm{N}_{2},\) (b) \(\mathrm{SO}_{2}\) or \(\mathrm{CO}_{2},\) (c) HF or HI?

Short Answer

Step by step solution

Understanding the Concept

Exercise Part (a) O2 or N2

Exercise Part (b) SO2 or CO2

Exercise Part (c) HF or HI

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