Question

Use bond-dissociation enthalpies (Table 4-2, p.203) to calculate values ofΔHfor the following reactions.

(a)

(b)

(c)

(d)

(e)

Short answer

(a) ΔH = -36kJ/mol

(b) ΔH = -17kJ/mol

(c) ΔH = -19kJ/mol

(d) ΔH= -54kJ/mol

(e) ΔH = -41kJ/mol

Step-by-step solution

Bond dissociation enthalpy (BDE)

It may be defined as the amount of enthalpy required to break a bond homolytically in such a way that each bonded atom retains one of the bond’s two electrons.

Mathematically, ΔH^o = ∑ (BDE of bonds broken) - ∑ (BDE of bonds formed)

Calculation of  ΔH

(a)

Hence, ΔH value for the reaction is ΔH = -36kJ/mol.

(b)

Hence, ΔH value for the reaction is ΔH = -17kJ/mol.

(c)

Hence, ΔH value for the reaction is ΔH = -19kJ/mol.

(d)

Hence, ΔHvalue for the reaction is ΔH= -54kJ/mol.

(e)

Hence, ΔH value for the reaction is ΔH = -41kJ/mol.