Among the following for which reaction heat of reaction represents bond energy of HCl

Options

A. `HCl(g)rarr H^(+)(g)+Cl^(-1)(g)`
B. `HCl(g)rarr 1//2 H_(2)(g)+1//2Cl_(2)(g)`
C. `2HCl(g)rarr H_(2)(g)+Cl_(2)(g)`
D. `HCl(g)rarr H(g)+Cl(g)`

Answer

To determine which reaction's heat of reaction represents the bond energy of HCl, we need to analyze the bond dissociation process involved in forming HCl from its constituent elements.

### Step-by-Step Solution:

1. **Identify the Formation of HCl**:
The bond energy of HCl can be represented by the reaction where hydrogen gas (H₂) and chlorine gas (Cl₂) combine to form hydrogen chloride (HCl). The balanced chemical equation for this reaction is:
\[ \frac{1}{2} H_2(g) + \frac{1}{2} Cl_2(g) \rightarrow HCl(g) \]

2. **Understanding Bond Energy**:
The bond energy of HCl is defined as the energy required to break one mole of HCl into its constituent atoms, which can be represented by the reverse of the formation reaction:
\[ HCl(g) \rightarrow \frac{1}{2} H_2(g) + \frac{1}{2} Cl_2(g) \]
The heat of reaction for this process will be equal to the bond energy of HCl.

3. **Heat of Reaction**:
The heat of reaction (ΔH) for the formation of HCl from its elements is approximately -92 kJ/mol. This negative sign indicates that the reaction is exothermic, meaning energy is released when HCl is formed.

4. **Conclusion**:
Therefore, the reaction that best represents the bond energy of HCl is the one that shows the formation of HCl from its elements, specifically:
\[ \frac{1}{2} H_2(g) + \frac{1}{2} Cl_2(g) \rightarrow HCl(g) \]
The correct option from the choices provided is the fourth option.