Enthalpy change for reaction
`1//2H_(2)(g)+1//2Cl_(2)(g)toHCl(g)` is called :-

Options

A. Enthalpy of combustion
B. Enthalpy of solution
C. Enthalpy of formation
D. Enthalpy of fusion

Answer

To determine the enthalpy change for the reaction:

\[ \frac{1}{2} H_2(g) + \frac{1}{2} Cl_2(g) \rightarrow HCl(g) \]

we need to identify what this enthalpy change represents. Let's analyze the reaction step by step.

### Step 1: Understand the Reaction
The reaction involves the formation of hydrogen chloride (HCl) gas from its elements, hydrogen (H2) and chlorine (Cl2).

### Step 2: Define Enthalpy of Formation
The enthalpy change associated with the formation of one mole of a compound from its elements in their standard states is known as the standard enthalpy of formation.

### Step 3: Identify the Components
In this case:
- The reactants are \(\frac{1}{2} H_2(g)\) and \(\frac{1}{2} Cl_2(g)\).
- The product is \(HCl(g)\).

### Step 4: Relate to Enthalpy of Formation
Since the reaction describes the formation of one mole of HCl from its constituent elements in their standard states, it is classified as the standard enthalpy of formation of HCl.

### Conclusion
Thus, the enthalpy change for the given reaction is called the **enthalpy of formation**.

### Final Answer
The correct option is **C: Enthalpy of formation**.

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