Name the unit in which the calorific value of a fuel is expressed.

Explanation

**Step-by-Step Solution:**

1. **Understanding Calorific Value**: The calorific value of a fuel refers to the amount of heat energy produced when a certain amount of fuel is completely burned (combusted).

2. **Unit of Measurement**: The calorific value is expressed in terms of energy per unit mass of the fuel.

3. **Identifying the Unit**: The standard unit used to express the calorific value of a fuel is "kilojoules per kilogram" (kJ/kg).

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