Question

Classify each substance based on the intermolecular forces present in that substance. 

A Dipole-dipole and dispersion only 

B. dispersion only 

C. Hydrogen bonding, dipole-dipole, and dispersion 

H₂O 

HCI 

CO

CH₄

Answer 1

• H2O -     Water molecules have all Hydrogen bonding, dipole- dipole and dispersion forces present among them. They are polar molecules which have dipole moments thus exhibiting strong dipole- dipole interactions. Also intermolecular hydrogen bonding is possible within water molecules where O atom of one molecule associates with an H atom of another water molecule.

ANSWER:   C

• HCl    -      These molecules exhibit dipole- dipole and dispersion forces only. Being polar molecules, they exhibit strong dipole- dipole interactions and dominate the weak dispersion forces that exist.

ANSWER:   A

• CO    -       These molecules also exhibit dipole- dipole and dispersion forces only. They are also polar molecules, exhibiting dipole- dipole interactions.

ANSWER:   A

• CH4   -       These molecules exhibit dispersion forces only. The molecule has a perfect tetrahedral structure and cancels out any dipole moment that generates because of small electronegativity difference between C and H atoms, ressulting in a molecule with zero net dipole moment. Hence methane molecules only exhibit weak dispersion forces.

ANSWER:   B