Question

1. consider the molecules represented above and the data in the table below. nonane and 2,3,4 - trifluoropentane have almost identical molar masses, but nonane has a significantly higher boiling point. which of the following statements best helps explain this observation? (a) the c - f is easier to break than the c - h bond. (b) the c - f is more polar than the c - h bond. (c) the carbon chains are longer in nonane than they are in 2,3,4 - trifluoropentane. (d) the carbon chains are farther apart in a sample of nonane than they are in 2,3,4 - trifluoropentane. 6. in which of the following liquids do the intermolecular forces include dipole - dipole forces? (a) f₂(l) (b) ch₄(l) (c) cf₄(l) (d) ch₂f₂(l) 7. which of the following is the strongest type of interaction that occurs between the atoms within the circled areas of the two molecules represented above? (a) polar covalent bond (b) nonpolar covalent bond (c) hydrogen bond (d) london dispersion forces

Explanation:

• Question 5:
• Nonane has a longer carbon chain. Longer carbon chains in nonane lead to stronger London dispersion forces (a type of intermolecular force). Stronger intermolecular forces require more energy (higher temperature) to overcome, resulting in a higher boiling point.
• Option A: Bond - breaking (related to chemical reactions) is not relevant to boiling point (a physical property).
• Option B: While C - F is polar, the overall effect of the longer carbon chain in nonane on intermolecular forces (London dispersion forces) is more significant for the boiling - point difference.
• Option D: The distance between carbon chains (if farther apart) would imply weaker intermolecular forces, which would lead to a lower boiling point, contrary to the observation.
• Question 6:
• Dipole - dipole forces occur in polar molecules.
• \(F_2(l)\) is non - polar (symmetrical, same atoms). \(CH_4(l)\) is non - polar (tetrahedral, symmetrical). \(CF_4(l)\) is non - polar (tetrahedral, symmetrical). \(CH_2F_2(l)\) is polar (as the bond dipoles do not cancel out due to its structure).
• Question 7:
• The circled areas show \(N - H\cdots O\) and \(N - H\cdots N\) interactions. Hydrogen bonding occurs when a hydrogen atom is bonded to a highly electronegative atom (like \(N\) or \(O\)) and interacts with another electronegative atom.
• Polar covalent bonds are within a single molecule (intramolecular), while we are looking at interactions between molecules (intermolecular). Non - polar covalent bonds are also intramolecular. London dispersion forces are weaker than hydrogen bonds.

Answer:

• Question 5: C. The carbon chains are longer in nonane than they are in 2,3,4 - trifluoropentane.
• Question 6: D. \(CH_2F_2(l)\)
• Question 7: C. Hydrogen bond