The energy value of petrol can be determined by

Analysis

The question asks for the specific laboratory apparatus used to measure the energy content (heat of combustion) of a fuel like petrol.

Concept Explanation

In chemistry, the heat of combustion is the amount of heat energy released when a specific amount of a substance is burned completely in oxygen. To measure this accurately, we use a device called a calorimeter.

Specifically, for fuels like petrol, which are volatile and release a large amount of energy, we use a Bomb calorimeter.

• How it works: A known mass of the fuel is placed in a sealed, strong steel container (the "bomb") filled with pure oxygen. This bomb is submerged in a known volume of water. The fuel is ignited electrically, and the heat released is absorbed by the water. By measuring the temperature change of the water, we can calculate the energy value of the fuel using the formula: $q = mc\Delta T$.

Step-by-Step Solution

1. Evaluate Option A (Bomb calorimeter): This is a constant-volume calorimeter used specifically to measure the heat of combustion of substances. It is the standard tool for determining the energy value of fuels.
2. Evaluate Option B (Catalytic cracker): This is an industrial unit used in petroleum refineries to break down heavy hydrocarbons into lighter, more valuable products like petrol. It is not a measuring instrument.
3. Evaluate Option C (Fractionating column): This is used in the process of fractional distillation to separate crude oil into different components based on their boiling points. It does not measure energy.
4. Evaluate Option D (Thermometer): While a thermometer is a part of a calorimeter used to measure temperature change, it is not the complete apparatus used to determine the energy value of a fuel on its own.

Conclusion

The Bomb calorimeter is the correct apparatus designed for this purpose.

Exam Tip: Whenever you see questions about "heat of combustion" or "energy value" of fuels in your JAMB or WASSCE exams, always look for "calorimeter." If the fuel is a solid or liquid, "Bomb calorimeter" is the specific type you need to identify.