Question

Angle between double bond and single bond compared with angle between single bond and single bond

Answer 1

Strength of sigma bond is more than that of a π-bond. A double bond in a diatomic molecules has a higher bond energy than a single bond and a triple bond has a higher bond energy than a double bond between the same atoms. C ≡ C > C = C > C – C (decreasing bond length)

Answer 2

A bond angle is the angle created by at least two bonds between three atoms.

Explanation:

The bond angle is influenced by the presence at the central atom of a lone pair of electrons. A lone pair of electrons often attempt to repel the mutual pair (bonded pair) of electrons at the central atom. Because of this, the bonds are slightly displaced within resulting in lower bond angle.

Bond angles of each of the molecules:

CH4 = 109.28 degree ( zero lone pair)

NH3 = 107  degree (one lone pair)

H2O = 104.5 degree  (2 lone pairs)

BF3 = 120 degree ( zero lone pair )

It is evident that molecules with less number of lone pair have greater bond anle but in CH4 and BF3 have zero lone pair. In CH4 there are 4 bond pairs and no lone pair of electrons while in BF3 there are 3 bond pairs and so no lone pairs.

Hence, the increasing order of bond angle is H2O <  NH3 <  CH4 <  BF3 .