Question

What type of intermolecular interaction predominates in each substance? a. HBr b. SiF4 NH4oh

Answer 1

a) HBr is a highly polar molecule. Hence dipole-dipole interaction is present. Some dispersion forces are also present. And there is a slight hydrogen bonding is also possible between HBr molecules.

b) SiF4: It is although a tetrahedral molecule the bond dipole cancels each other and hence molecule becomes non-polar.

Hence there is only dispersion forces working between the molecules.

c) NH4OH: NH4OH is an ionic compound. N-H and O-H bonds are highly polar bonds present in this molecule. Hence there is strong ionic bonding is present. There are other forces as well present. However, the strongest force is ionic bonding.

An easy way to summarise this:

Interacting molecules or ions NO NC YES NO Are polar molecules involved? Are ions involved? Are polar molecules and ions both present? YES YES Are hydrogen atoms bonded to N, O, or F atoms? NO YES Dispersion forces only (induced dipoles) Dipole-dipole forces Hydrogen bonding Ion-dipole forces Ionic bonding (Section 8.2) Examples: Ar(1), 12(s) Examples: H,S, CH,CI Examples: liquid, and solid H2O, NH3, HF Examples: KBr in HO Examples: NaCI, NH4NO3 van der Waals forces Ton-induced dipole and dipole-induced dipole are additional types of dispersion forces.