Quiz 2

Four different liquid compounds in flasks at 20°C are placed in flasks. The liquid in flask C, has the most particles in the vapor phase. This table gives information on each compound present but does not say which substance is in which flask. Which of the following is NOT SHOWN in the flask models, but BEST HELPS EXPLAIN why flask C must contain pentane?

• The random motion of the particles within the liquids.

• The relative speeds of the vapor particles in each flask.

• The strength of the intermolecular forces between the particles in the liquids.

• The atomic radius of each particle in the flask.

The diagrams below represent two gas samples in identical containers at the same temperature. Each circle represents a gas particle, and the particles in each sample are assumed to have the same molar mass. Which of the following statements MOST ACCURATELY compares the density of the two gas samples?

• The density of gas in Gas B is twice that of Gas A because it has twice as many particles in the same volume.

• The density of Gas B is higher than Gas A because it has fewer particles, leaving more space for movement.

• The densities of the two gas samples are the same because they are the same molar mass and temperature.

• The density cannot be evaluated without knowing the exact quantity of the molar mass for each gas.

A particle-level diagram of a metallic compound is shown below. The BEST EXPLANATION for how electrons behave in metallic bonds between metal atoms is...

• electrons are equally shared between metal cation cores due to the similar high electronegativities between different metals in the compound.

• electrons are unequally shared and form a dipole between metal cation cores due to a large difference in electronegativity between different metals in the compound.

• electrons are delocalized between metal cation cores due to similar low electronegativities between different metals in the compound.

• electrons are delocalized between metal cation cores due to similar high electronegativities between different metals in the compound.

The Lewis structure of methyl acetate is shown below. Which of the following identifies ALL of the intermolecular forces present among molecules of methyl acetate?

• London dispersion forces only

• Dipole-dipole interactions only

• London dispersion forces and dipole-dipole interactions

• London dispersion forces and hydrogen bonding

Formic acid is shown. In the vapor phase, formic acid exists as a dimer (complexes consisting of two formic acid molecules) rather than individual molecules. The formic acid dimer is held together by two hydrogen bonds. Which of the following diagrams correctly represents the hydrogen bonding (denoted by dotted lines) in the formic acid dimer?

• A

• B

• C

• D

Diatomic iodine has a much higher boiling point than water. A table comparing these two molecules is below. Which justification below is the BEST EXPLANATION as to why the boiling point for water is lower than iodine?

• Water exhibits hydrogen bonding, which is a very weak intermolecular force, and iodine does not.

• Iodine molecules have a much larger size and more electrons than water molecules, leading to stronger London dispersion forces that outweigh water's hydrogen bonds.

• Each iodine atom alone is a highly electronegative atom, which means the bond between two iodine atoms will cause very strong dipole-dipole forces that are stronger than the hydrogen bonding in water.

• Water molecules are smaller and cannot form strong intermolecular forces, leading to a lower boiling point than iodine.

Which of the following Lewis diagrams BEST REPRESENTS the bonding in the N₂O molecule, considering formal charges?

• Option A

• Option B

• Option C

• Option D

A butane molecule is shown below. Which of the following is an ISOMER of butane?

• 
• 
• 
• 

SELECT the molecule that contains the MOST accurately drawn net dipole moment for the molecule.

• A

• B

• C

• D

Based on these structures, which isomer of 1,2-dichloroethylene has the HIGHER MELTING POINT and why?

• Isomer 1 has a higher melting point because Isomer 1 has a molecular dipole and Isomer 2 does not.

• Isomer 1 has a higher melting point because Isomer 1 atoms are more compact than those of Isomer 2.

• Isomer 2 has a higher melting point because Isomer 2 forms hydrogen bonds, while Isomer 1 does not.

• Isomer 2 has a higher melting point because Isomer 2 has stronger London dispersion forces than Isomer 1.