What kind of intermolecular forces act between a nitrosyl chloride NOCl molecule and an oxide O2- anion?
Note: If there is more than one type of intermolecular force that acts, be sure to list them all, with a comma between the name of each force.
The Correct Answer and Explanation is:
Answer:
Ion-dipole forces, dipole-induced dipole forces
Explanation:
Intermolecular forces are attractions between molecules or ions that determine many physical properties such as boiling point, solubility, and melting point. To identify the forces acting between a nitrosyl chloride (NOCl) molecule and an oxide anion (O²⁻), we must analyze their nature and interactions.
1. Nature of the Species:
- NOCl molecule:
NOCl is a polar molecule. It has a permanent dipole moment because the atoms have different electronegativities, and the molecule is not symmetrical. The nitrogen, oxygen, and chlorine atoms create a bond dipole due to differences in electron distribution. This means NOCl has a permanent dipole. - O²⁻ ion:
The oxide ion carries a full negative charge (2-), making it a strongly charged species (an anion). This charge is localized, not spread out like a dipole. It is much stronger than dipoles or induced dipoles.
2. Types of Intermolecular Forces Present:
- Ion-Dipole Forces:
The strongest interaction between a charged ion and a polar molecule is the ion-dipole force. Here, the negatively charged oxide ion (O²⁻) will attract the partial positive end of the NOCl molecule’s dipole. This interaction is electrostatic and stronger than most other intermolecular forces. Ion-dipole forces are typical in solutions where ions interact with polar solvents (e.g., NaCl dissolved in water). - Dipole-Induced Dipole Forces:
The oxide ion, being highly charged, can also induce a dipole in the electron cloud of the NOCl molecule (if we consider temporary distortions in electron density). Conversely, the polar NOCl molecule can induce a dipole in the electron cloud of the oxide ion’s surroundings or other molecules nearby. This results in dipole-induced dipole interactions, which are generally weaker than ion-dipole forces but can coexist.
3. Other Forces Not Present:
- Hydrogen bonding: NOCl has no hydrogen atom bonded to highly electronegative atoms (N, O, or F), so hydrogen bonding is not applicable.
- London Dispersion Forces: While these are always present, they are negligible compared to the strong ion-dipole interactions here.
- Dipole-Dipole Forces: These act between polar molecules but not between a molecule and an ion.
Summary:
Between NOCl and O²⁻, the primary intermolecular force is ion-dipole because a charged ion interacts strongly with a polar molecule. Additionally, dipole-induced dipole forces may be present but are weaker. These combined forces govern how these species interact in a mixture or solution.
