Question

Place the following compounds in order of increasing strength of intermolecular forces. Ch4 ch3ch2ch3 ch3ch3

Answer 1

Explanation:

More is the mass of an alkane molecule more will be its boiling point. This means that forces of attraction will be more when mass is more as more heat is required to break the bonds within atoms. Hence, boiling point is more.

Therefore, in the given molecules mass of $CH_{4}$ is 16.04 g/mol, mass of $CH_{3}CH_{2}CH_{3}$ is 44 g/mol, and mass of $CH_{3}CH_{3}$ is 30 g/mol.

Thus, we can see that $CH_{3}CH_{2}CH_{3}$ has the highest mass and $CH_{4}$ has least mass.

Hence, increasing strength of intermolecular forces of given compounds is as follows.

             $CH_{4} < CH_{3}CH_{3} < CH_{3}CH_{2}CH_{3}$          

Answer 2

Answer:

CH4 < CH3CH3 < CH3CH2CH3

Explanation:

Alkanes are the simplest hydrocarbons (compounds of C and H), they have no functional group and the bonds between carbon atoms (with sp3 hybridization) are simple bonds, each orbital is directed to the vertices of a tetrahedron. Each orbital forms a σ bond with each H.

Alkanes may have a straight or branched chain. When the compounds have the same molecular form and only differ in the order in which the atoms in the molecule are linked, they are called constitutional or structural isomers.

The interaction between molecules (intermolecular forces) is a balance between the repulsion of the external electrons and the attraction of the nuclei of a molecule on the electrons of which they are close.

Alkanes without electronegative atoms have a relatively dense and continuous "shell" of electrons. The repulsion of electronic clouds is important and therefore the attraction between alkane molecules is very weak.

The "shape" of the molecules affects the contact surface. What do these experimental data suggest? Unbranched molecules, with linear zigzag structure, attract more effectively.

In other words, the longer the C chain in alkanes increases the intermolecular forces.