The enthalpy change for the reaction `2C("graphite")+3H_(2)(g)rarrC_(2)H_(6)(g)` is called

Options

A. Enthalpy of formation
B. Enthalpy of combustion
C. Enthalpy of hydrogenation
D. Enthalpy of vaporisation

Answer

To determine the enthalpy change for the reaction

\[ 2C(\text{graphite}) + 3H_2(g) \rightarrow C_2H_6(g) \]

we need to identify what this enthalpy change is called.

### Step-by-Step Solution:

1. **Identify the Reaction**: The given reaction involves the formation of ethane (C2H6) from its constituent elements, which are carbon (in the form of graphite) and hydrogen (in the form of hydrogen gas).

2. **Understand Enthalpy Change**: The enthalpy change associated with the formation of a compound from its elements in their standard states is known as the enthalpy of formation.

3. **Standard States**: In this reaction, carbon is in its standard state as graphite, and hydrogen is in its standard state as H2 gas. This is important because the enthalpy of formation is defined based on the elements being in their standard states.

4. **Conclusion**: Since the reaction describes the formation of ethane from its elements in their standard states, the enthalpy change for this reaction is called the "enthalpy of formation" of ethane.

### Final Answer:
The enthalpy change for the reaction \( 2C(\text{graphite}) + 3H_2(g) \rightarrow C_2H_6(g) \) is called the **enthalpy of formation** of ethane.

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