Question

select the arrangement that orders the compounds by increasing boiling point based on predominant intermolecular force.

\\(\text{ch}_4 < \text{c}_4\text{h}_{10} < \text{nf}_3 < \text{h}_2\text{o}\\)
\\(\text{ch}_4 < \text{c}_4\text{h}_{10} < \text{h}_2\text{o} < \text{nf}_3\\)
\\(\text{h}_2\text{o} < \text{nf}_3 < \text{c}_4\text{h}_{10} < \text{ch}_4\\)
\\(\text{c}_4\text{h}_{10} < \text{ch}_4 < \text{nf}_3 < \text{h}_2\text{o}\\)

Explanation:

Identify predominant intermolecular forces

Using the Intermolecular Forces knowledge point

• \(\text{CH}_4\): Nonpolar molecule, predominant force is London Dispersion Forces.
• \(\text{C}_4\text{H}_{10}\): Nonpolar molecule, predominant force is London Dispersion Forces.
• \(\text{NF}_3\): Polar molecule, predominant force is Dipole-Dipole Interactions.
• \(\text{H}_2\text{O}\): Polar molecule with \(\text{O-H}\) bonds, predominant force is Hydrogen Bonding.

Compare dispersion forces by molecular size

Using the London Dispersion Forces knowledge point

• Both \(\text{CH}_4\) and \(\text{C}_4\text{H}_{10}\) exhibit dispersion forces.
• \(\text{C}_4\text{H}_{10}\) has a larger molar mass and electron cloud than \(\text{CH}_4\).
• Larger electron clouds are more polarizable, leading to stronger dispersion forces.
• Therefore, the boiling point of \(\text{CH}_4\) is lower than that of \(\text{C}_4\text{H}_{10}\):

$$\text{CH}_4 < \text{C}_4\text{H}_{10}$$

Rank by relative strength of force types

Using the Dipole-Dipole Interactions and Hydrogen Bonding knowledge points

• London Dispersion Forces (in small/medium molecules) < Dipole-Dipole Interactions < Hydrogen Bonding.
• \(\text{NF}_3\) (dipole-dipole) has stronger forces than the nonpolar hydrocarbons.
• \(\text{H}_2\text{O}\) (hydrogen bonding) has the strongest intermolecular forces among the group.
• This yields the relative order:

$$\text{Dispersion} < \text{Dipole-Dipole} < \text{Hydrogen Bonding}$$

Establish the final increasing order

Using the Boiling Point Trends knowledge point

• Combining the individual comparisons:

$$\text{CH}_4 < \text{C}_4\text{H}_{10} < \text{NF}_3 < \text{H}_2\text{O}$$

Answer:

• (A) \(\text{CH}_4 < \text{C}_4\text{H}_{10} < \text{NF}_3 < \text{H}_2\text{O}\) (Correct answer)
• (B) \(\text{CH}_4 < \text{C}_4\text{H}_{10} < \text{H}_2\text{O} < \text{NF}_3\)
• (C) \(\text{H}_2\text{O} < \text{NF}_3 < \text{C}_4\text{H}_{10} < \text{CH}_4\)
• (D) \(\text{C}_4\text{H}_{10} < \text{CH}_4 < \text{NF}_3 < \text{H}_2\text{O}\)