Calorific values of fuels are generally expressed in which of the following units ?

Options

A. Calories/gram
B. Kilocalories/kg
C. Joule
D. Kilojoules/kg

Explanation

To solve the question regarding the units in which calorific values of fuels are expressed, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Calorific Value**:
- Calorific value refers to the amount of heat energy produced when a certain amount of fuel is completely burned. It is an important property of fuels.

2. **Identify the Components**:
- The calorific value is determined by the heat produced during combustion and the mass of the fuel being burned.

3. **Determine the Units of Measurement**:
- The unit of heat is typically expressed in joules (J) or kilojoules (kJ).
- The mass of the fuel is measured in kilograms (kg).

4. **Combine the Units**:
- Since calorific value is defined as the heat produced per unit mass of fuel, the appropriate unit for calorific value can be expressed as:
\[ \text{Calorific Value} = \frac{\text{Heat (in kJ)}}{\text{Mass (in kg)}} = \text{kJ/kg} \]

5. **Select the Correct Option**:
- From the options given in the question, we look for the unit that matches our derived unit of kJ/kg.
- The correct option is **kilo joule per kg (kJ/kg)**.

### Final Answer:
The calorific values of fuels are generally expressed in **kilo joule per kg (kJ/kg)**.

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