Question

Which is the correct order of bond energy of single, double and triple bonds between carbon atoms?
A. ${{C}} - {{C}} > {{C}} = {{C}} > {{C}} \equiv {{C}}$
B. ${{C = C}} > {{C}} \equiv {{C > C}} = {{C}}$
C. ${{C}} \equiv {{C}} > {{C - C > C}} = {{C}}$
D. ${{C}} \equiv {{C}} > {{C}} = {{C}} > {{C - C}}$

Answer 1

Hint:When a bond is broken, energy is released. This energy is known as bond dissociation energy. It depends upon the bond length, bond order and bond strength. Bond energy changes when the number of bonds between the atoms is changed.

Complete answer:
Bond energy is the energy to break a bond between two atoms. Bond energy is influenced by the bond order. Bond order is related to the number of bonds and the bonding pairs.
In ${{C}} - {{C}}$ bond, the number of bonds is one and the number of bonding pairs is one. Thus the bond order is one. In ${{C = C}}$ bond, the number of bonds is two and the number of bonding pairs is one. Its bond order is two. In ${{C}} \equiv {{C}}$ bond, there are three numbers of bonds and one bonding pair. Thus its bond order is three. Bond energy is directly proportional to the bond order.
It also depends upon the strength of the bond. In ${{C}} - {{C}}$ bond, there is only one $\sigma $ bond. While in ${{C = C}}$ bond, there is one $\sigma $ bond and one $\pi $ bond. In ${{C}} \equiv {{C}}$ bond, there is one $\sigma $ bond and two $\pi $ bonds. $\pi $ bond is more stronger than $\sigma $ bond. Thus, more number of $\pi $ bonds means stronger will be the bond. Thus ${{C}} \equiv {{C}}$ bond will be stronger than ${{C = C}}$ bond and ${{C}} - {{C}}$ bond. Moreover, ${{C = C}}$ is stronger than ${{C}} - {{C}}$ bond.
When the bond is stronger, it is difficult to break.
Thus the order of bond energy is given below:
${{C}} \equiv {{C}} > {{C}} = {{C}} > {{C - C}}$

Hence, the correct option is D.

Additional information:
The bond energy of ${{C}} - {{C}}$ bond is $346{{kJ}}.{{mo}}{{{l}}^{ - 1}}$, ${{C = C}}$ bond-$602{{kJ}}.{{mo}}{{{l}}^{ - 1}}$ and ${{C}} \equiv {{C}}$ bond is $835{{kJ}}.{{mo}}{{{l}}^{ - 1}}$.

Note:
Bond energy is similar to the bond length. Bond length is directly proportional to the bond energy. In ${{C}} - {{C}}$ bond, bond length is very high. Bond length in ${{C}} \equiv {{C}}$ bond is lower than that in ${{C = C}}$ whose bond length is lower than that in ${{C}} - {{C}}$ bond.