Heat of combustion of `CH_(4),C_(2)H_(6), C_(2)H_(4)` and `C_(2)H_(2)` gases are -212.8, -212.8, -373.0, -337.0 and -310.5 Kcal respectively at the same temperature. The best fuel among these gases is :

Options

A. `CH_(4)`
B. `C_(2)H_(6)`
C. `C_(2)H_(4)`
D. `C_(2)H_(2)`

Answer

To determine the best fuel among the given gases based on their heat of combustion values, we can follow these steps:

### Step 1: Understand the Heat of Combustion
The heat of combustion is the amount of energy released when a substance is completely burned in oxygen. It is usually expressed in kilocalories (Kcal) and is a measure of the calorific value of a fuel. A higher (less negative) value indicates a better fuel.

### Step 2: List the Given Values
The heat of combustion values for the gases are:
- Methane (CH₄): -212.8 Kcal
- Ethane (C₂H₆): -212.8 Kcal
- Ethylene (C₂H₄): -373.0 Kcal
- Acetylene (C₂H₂): -310.5 Kcal

### Step 3: Compare the Values
To find the best fuel, we need to compare the absolute values of the heat of combustion:
- Methane: 212.8 Kcal
- Ethane: 212.8 Kcal
- Ethylene: 373.0 Kcal
- Acetylene: 310.5 Kcal

### Step 4: Identify the Best Fuel
Among the gases, methane and ethane have the same heat of combustion value, which is the least negative (or highest calorific value). However, since the question asks for the best fuel, we can conclude that methane (CH₄) is often considered the best fuel due to its higher efficiency and lower emissions compared to ethane.

### Conclusion
Thus, the best fuel among the given gases is **Methane (CH₄)**.

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