Question

rank the compounds from lowest to highest boiling point and explain your answer. 41. in each of the following groups of substances, pick the one that has the given property. justify your answer. a. highest boiling point: hbr, kr, or cl2 b. highest freezing point: h2o, nacl, or hf c. lowest vapor pressure at 25°c: cl2, br2, or i2 d. lowest freezing point: n2, co, or co2 e. lowest boiling point: ch4, ch3ch3, or ch3ch2ch3 f. highest boiling point: hf, hcl, or hbr. unless otherwise noted, all art on this page is © cengage learning 2014.

Explanation:

Step1: Understand intermolecular forces

Intermolecular forces (IMF) such as London - dispersion forces, dipole - dipole forces, and hydrogen bonding affect boiling point, freezing point, and vapor pressure. London - dispersion forces are present in all molecules and increase with molar mass. Hydrogen bonding is a strong type of dipole - dipole force.

Step2: Analyze part a

HBr is a polar molecule with dipole - dipole forces and London - dispersion forces. Kr is a non - polar noble gas with only London - dispersion forces. Cl₂ is a non - polar molecule with only London - dispersion forces. HBr has the highest boiling point because dipole - dipole forces are stronger than London - dispersion forces for molecules of similar molar mass.

Step3: Analyze part b

H₂O has hydrogen bonding, dipole - dipole forces, and London - dispersion forces. NaCl is an ionic compound with strong ionic bonds. HF has hydrogen bonding, dipole - dipole forces, and London - dispersion forces. NaCl has the highest freezing point due to the strong ionic bonds.

Step4: Analyze part c

Vapor pressure is inversely related to intermolecular forces. Cl₂, Br₂, and I₂ are non - polar molecules with only London - dispersion forces. The molar mass increases from Cl₂ to I₂. I₂ has the strongest London - dispersion forces and the lowest vapor pressure.

Step5: Analyze part d

N₂ is a non - polar molecule with only London - dispersion forces. CO is a polar molecule with dipole - dipole forces and London - dispersion forces. CO₂ is a non - polar molecule with only London - dispersion forces. N₂ has the lowest freezing point as it has the weakest intermolecular forces.

Step6: Analyze part e

CH₄, CH₃CH₃, and CH₃CH₂CH₃ are non - polar hydrocarbons with only London - dispersion forces. The molar mass increases from CH₄ to CH₃CH₂CH₃. CH₄ has the lowest boiling point as it has the weakest London - dispersion forces.

Step7: Analyze part f

HF has hydrogen bonding, dipole - dipole forces, and London - dispersion forces. HCl and HBr are polar molecules with dipole - dipole forces and London - dispersion forces. HF has the highest boiling point due to hydrogen bonding.

Answer:

a. HBr
b. NaCl
c. I₂
d. N₂
e. CH₄
f. HF