Given the following standard heats of reactions:
(a) heat of formation of water `= -68.3 kcal`, (b) heat of combustion of `C_(2)H_(2) =- 310.6 kcal`, (c ) heat of combustion of ethylene `=- 337.2 kcal`. Calculate the heat of reaction for the hydrogenation of acetylene at constant volume and at `25^(@)C`.

Explanation

To calculate the heat of reaction for the hydrogenation of acetylene at constant volume and at 25°C, we can follow these steps:

### Step 1: Write the Reaction
The hydrogenation of acetylene (C₂H₂) can be represented as:
\[ \text{C}_2\text{H}_2(g) + \text{H}_2(g) \rightarrow \text{C}_2\text{H}_4(g) \]

### Step 2: Identify the Given Data
We have the following standard heats of reactions:
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