Classify each substance based on the intermolecular forces present in that substance. Hydrogen bonding; dipole-dipole, and dispersion Dipole-dipole and dispersion only Dispersion only HF Hz HCI CO Answer Bank
The Correct Answer and Explanation is:
molecular structures and the types of bonding and polarity they exhibit. The three key types of IMFs are:
- Dispersion forces (also called London forces): Present in all molecules, especially nonpolar ones.
- Dipole-dipole interactions: Occur in molecules with a permanent dipole (polar molecules).
- Hydrogen bonding: A special, stronger dipole-dipole interaction occurring when hydrogen is bonded directly to nitrogen (N), oxygen (O), or fluorine (F).
Substance Classification
| Substance | Intermolecular Forces Present |
|---|---|
| HF (Hydrogen fluoride) | Hydrogen bonding, dipole-dipole, and dispersion |
| H₂ (Hydrogen gas) | Dispersion only |
| HCl (Hydrogen chloride) | Dipole-dipole and dispersion only |
| CO (Carbon monoxide) | Dipole-dipole and dispersion only |
Explanation
Intermolecular forces are essential in determining the physical properties of substances, such as boiling point, solubility, and phase changes. Every molecule experiences dispersion forces, the weakest IMF, caused by temporary shifts in electron density. These are especially significant in nonpolar molecules like H₂ (hydrogen gas), which is symmetrical and lacks any permanent dipole, making dispersion the only force acting between H₂ molecules.
Hydrogen fluoride (HF) is a polar molecule where hydrogen is directly bonded to fluorine, a highly electronegative atom. This allows for hydrogen bonding, a strong IMF. HF also exhibits dipole-dipole interactions due to its permanent dipole, and dispersion forces, like all molecules. Therefore, HF has all three types of IMFs.
Hydrogen chloride (HCl) is also a polar molecule, but since hydrogen is bonded to chlorine (not N, O, or F), it does not qualify for hydrogen bonding. Instead, it exhibits dipole-dipole interactions and dispersion forces.
Carbon monoxide (CO), despite being composed of two nonmetals, is a polar molecule due to the difference in electronegativity between carbon and oxygen. Thus, CO experiences dipole-dipole interactions and dispersion forces. However, the hydrogen atom is not present and hydrogen bonding does not occur here either.
In summary, identifying the types of intermolecular forces involves understanding molecular polarity and recognizing conditions for hydrogen bonding. This classification helps explain trends in boiling points, solubility, and other physical behaviors of substances.
