Question

Rank the indicated bonds in order of increasing bond dissociation energy.

Short answer

Answer

The bond dissociation energy increases in the order:$\mathrm{I}-{\mathrm{CCl}}_3<\mathrm{Br}-{\mathrm{CCl}}_3<\mathrm{Cl}-{\mathrm{CCl}}_3$

Step-by-step solution

Step-by-Step SolutionStep 1: Bond dissociation Energy

The energy applied to dissociate a bond is called bond dissociation energy.

The bond dissociation energy is directly proportional to the strength of the bond.

Inorganic compounds, alkanes have the least bond dissociation energy. Alkenes have higher bond dissociation energy. In comparison, alkynes have the maximum bond dissociation energy.

Factors affecting Bond Dissociation Energy

There are various factors on which the amount of energy required to break the bonds depends. These factors are described hereunder:

• Bond length: Shorter the bond length, the greater is the strength of the chemical bond. Hence, Bond Dissociation energy is higher and vice-versa.

• The number of electrons shared: the number of electrons shared implies the number of chemical bonds existing between two atoms or groups.

Hence, the more the number of electrons is shared, the number of bonds and bond strength increases between two atoms. Hence, bond dissociation energy increases and vice-versa.

• Atomic size: the larger the atomic size, the more is the bond length. Hence, the bond strength is less, and so bond dissociation energy is also less.

Comparison of bond dissociation energy in the given compounds

In the given three structures, the three halogens, i.e., chlorine, iodine, and bromine, are bonded with a single bond to the same chemical moiety.

The basis of comparing the Bond Dissociation energy for the three given structures is the atomic size of the halogen atoms attached.

Among $\mathrm{Cl}-{\mathrm{CCl}}_3,\mathrm{Br}-{\mathrm{CCl}}_3\mathrm{and}\mathrm{I}-{\mathrm{CCl}}_3$, chlorine has the smallest size, bromine has the intermediate size, and iodine has the largest size. Hence, the Cl-C bond length is the smallest, Br-C bond length is intermediate, and I-C bond length is the largest. Comparison of bond lengths

Thus, the bond strength increases in the order: I-C < Br-C <Cl-C

Hence, the bond dissociation energy also has the same order as the bond strength as $\mathrm{I}-{\mathrm{CCl}}_3<\mathrm{Br}-{\mathrm{CCl}}_3<\mathrm{Cl}-{\mathrm{CCl}}_3$.