Hydrogen bonding occurs when a hydrogen atom bonded to N, O, or F is attracted to another molecule's N, O or F atom. Which of the following can participate in hydrogen bonding?

• CBr₄

• NO₂

• H₂S

• NH₃

Answer explanation

NH3 can participate in hydrogen bonding because it has a hydrogen atom bonded to nitrogen, which can attract other N, O, or F atoms. CBr4 and H2S do not have the necessary electronegative atoms, and NO2 does not have hydrogen bonded to N.

Tags

NGSS.HS-PS1-1

All molecules can exhibit London dispersion forces, but dipole-dipole and hydrogen bonding are stronger attractions for molecules with similar masses/numbers of electrons when they are present. Which of these can ONLY exhibit London dispersion forces?

• I₂

• NH₃

• OCl₂

• CH₃Cl

Answer explanation

I2 is a nonpolar molecule and can only exhibit London dispersion forces. In contrast, NH3, OCl2, and CH3Cl have polar characteristics, allowing them to engage in dipole-dipole interactions or hydrogen bonding.

Dipole-dipole attractions occur between polar molecules. Which of these molecules is polar?

• H₂

• HCl

• Cl₂

• Br₂

Answer explanation

HCl is a polar molecule due to the significant electronegativity difference between H and Cl, creating a dipole moment. In contrast, H2, Cl2, and Br2 are nonpolar as they consist of identical atoms with no charge separation.

Tags

NGSS.HS-PS1-1

The weaker the intermolecular forces of a substance, the _____________ the boiling point.

• higher

• lower

Answer explanation

The weaker the intermolecular forces, the less energy is required to separate the molecules. Therefore, the boiling point is lower when intermolecular forces are weak.

Tags

NGSS.HS-PS1-3

Which of the following has the highest boiling point?

• H₂

• NH₃

• N₂

• O₂

Answer explanation

NH3 has the highest boiling point due to hydrogen bonding, which is stronger than the dispersion forces present in H2, N2, and O2. This results in NH3 requiring more energy to transition to the gas phase.

Tags

NGSS.HS-PS1-3

Which of the following explains the relatively high melting and boiling point of water?

• Strong dipole-dipole attractions between water molecules

• Strong hydrogen bonds between water molecules

• London dispersion forces between water molecules

• Dipole-induced dipole attractions between water molecules

Answer explanation

Water's relatively high melting and boiling points are due to strong hydrogen bonds between its molecules. These bonds require significant energy to break, resulting in higher phase transition temperatures compared to substances with weaker interactions.

London dispersion forces are stronger between atoms or molecules with more electrons, and weaker between atoms or molecules with fewer electrons. Which of the following has the strongest London dispersion forces?

• F₂

• Br₂

• I₂

• Cl₂

Answer explanation

I₂ has the strongest London dispersion forces because it has the most electrons among the choices, leading to greater polarizability and stronger temporary dipoles compared to F₂, Cl₂, and Br₂.

Which of the following intermolecular forces can all types of particles exhibit?

• London dispersion forces

• dipole-dipole forces

• hydrogen bonding

• none of the above

Answer explanation

London dispersion forces are present in all types of particles, including nonpolar molecules, due to temporary dipoles. In contrast, dipole-dipole forces and hydrogen bonding require polar molecules or specific conditions.

A Lewis structure for carbon dioxide is shown below. What types of intermolecular attractions can be present between molecules of carbon dioxide in a pure CO₂ sample? Select all that apply

• London dispersion forces

• dipole-dipole attractions

• hydrogen bonds

• ion-dipole attractions

Answer explanation

In pure CO2, the molecules are nonpolar due to their linear shape, so dipole-dipole attractions and hydrogen bonds are not present. The only intermolecular attraction is London dispersion forces, which occur in all molecules.

Which of these molecules can participate in dipole-dipole attractions? Select all that apply.

• Br₂

• CF₄

• I₂

• PCl₃

• CO

Answer explanation

PCl3 and CO have permanent dipoles due to their polar bonds and molecular geometry, allowing them to participate in dipole-dipole attractions. Br2, CF4, and I2 are nonpolar and do not exhibit these attractions.