Question

Using the BDE values from Appendix 3, calculate the \(\Delta H_{\text {rxn }}^{0}\) value and state if the reaction below is exothermic or endothermic.

Short answer

Based on the given reaction A-B + C-D → A-C + B-D, following the step-by-step solution, calculate the change in enthalpy (\(\Delta H_{\text {rxn }}^0\)) by finding the BDE values for each of the four bonds: A-B, C-D, A-C, and B-D. Then, determine if the reaction is exothermic or endothermic.

Step-by-step solution

Determine bond types

In the given reaction A-B + C-D → A-C + B-D, we have 4 bonds: A-B, C-D, A-C and B-D. 2. Find the BDE values

Look up BDE values

Using Appendix 3, find the BDE values for all four bonds: A-B, C-D, A-C, and B-D. Let's represent them as \(BDE_{AB}\), \(BDE_{CD}\), \(BDE_{AC}\), and \(BDE_{BD}\), respectively. 3. Calculate the change in enthalpy

Calculate \(\Delta H_{\text {rxn }}^0\)

To find \(\Delta H_{\text {rxn }}^0\), we will subtract the BDE values of formed bonds from the BDE values of broken bonds: \(\Delta H_{\text {rxn }}^0 = (BDE_{AC} + BDE_{BD}) - (BDE_{AB} + BDE_{CD})\) 4. Determine if the reaction is exothermic or endothermic

Reaction type

If \(\Delta H_{\text {rxn }}^0\) is negative, the reaction is exothermic, meaning it releases energy. If \(\Delta H_{\text {rxn }}^0\) is positive, the reaction is endothermic, meaning it absorbs energy.