Question

Arrange the following molecules according to the strength of their dispersion forces.

Answer 1

Answer:

Dispersion force : is the weakest intermolecular force. The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make  form temporary dipoles. This force is also called an induced dipole-induced dipole attraction because one molecule induce dipole in other molecule. London forces are the attractive forces that cause non polar substances to condense to liquids and to freeze into solids when the temperature is lowered sufficiently.

Molecular size :

•Larger and heavier atoms and molecules exhibit stronger dispersion forces than  lighter and smaller ones.

•In a larger atom or molecule, the valence electrons are,  farther from the nuclei than in a smaller atom or molecule. They are less tightly bounded and can more easily form temporary dipoles.

Molecular shape:

•At room temperature, neopentane (C5H12) is a gas whereas n-pentane (C5H12) is a liquid.

•London dispersion forces between n-pentane molecules are stronger than those between neopentane molecules even though both molecules are nonpolar and have the same molecular weight.

•The somewhat cylindrical shape of n-pentane molecules allows them to come in contact with each other more effectively than the somewhat spherical neopentane molecules.

so here ,

    2 > 3 > 1 > 4 > 5 > 6

1st have more dispersion force because it is n heptane present in liquid form.

6th have lowest force because it is present in gaseous form.