The reaction S81g2 S 4 S21g2 has ΔH° = + 237 kJ(b) The average S ¬ S bond dissociation energy is 225 kJ/mol. Using the value of ΔH° given above, what is the S ' S double bond energy in S21g2?

Verified step by step guidance

1. Identify the reaction: \( S_8(g) \rightarrow 4S_2(g) \) with \( \Delta H^\circ = +237 \text{ kJ} \).
2. Recognize that the reaction involves breaking \( S-S \) single bonds in \( S_8 \) and forming \( S=S \) double bonds in \( S_2 \).
3. Calculate the total energy required to break all the \( S-S \) single bonds in \( S_8 \). Since there are 8 \( S-S \) bonds, use the bond dissociation energy: \( 8 \times 225 \text{ kJ/mol} \).
4. Determine the energy change for forming \( S=S \) double bonds in \( S_2 \). Since 4 \( S_2 \) molecules are formed, calculate the energy for 4 \( S=S \) bonds.
5. Use the equation \( \Delta H^\circ = \text{Energy to break bonds} - \text{Energy to form bonds} \) to solve for the \( S=S \) double bond energy.

Key Concepts

Bond Dissociation Energy

Bond dissociation energy (BDE) is the energy required to break a bond in a molecule, resulting in the formation of separate atoms or radicals. It is typically expressed in kJ/mol and reflects the strength of a chemical bond. In this question, the average S-S bond dissociation energy is given as 225 kJ/mol, which is crucial for calculating the energy associated with the S=S double bond.

Enthalpy Change (ΔH°)

Enthalpy change (ΔH°) is a measure of the heat content change during a chemical reaction at constant pressure. A positive ΔH° indicates that the reaction is endothermic, meaning it absorbs heat from the surroundings. In this case, the given ΔH° of +237 kJ provides essential information for determining the energy associated with the formation or breaking of bonds in the reaction.

Double Bond Energy

Double bond energy refers to the energy required to break a double bond between two atoms, which is typically greater than that of a single bond due to the additional shared pair of electrons. In this question, calculating the S=S double bond energy in S2(g) involves using the provided ΔH° and the average bond dissociation energy to find the specific energy associated with the double bond in sulfur.