Bomb Calorimeter – Definition, Uses, Equation

What is Calorimeter?

Calorimetry is the field of science that deals with the measurement of the state of a body with respect to the thermal aspects in order to examine its physical and chemical changes. In this topic, we will teach about bomb calorimeter, its definition, uses and equation.

The changes could be physical such as melting, evaporation etc. or could also be chemical such as burning, acid-base neutralization, etc. A calorimeter is what is used to measure the thermal changes of a body.

Calorimetry is used extensively in the fields of thermochemistry in calculating the enthalpy, stability, heat capacity, etc. A bomb calorimeter is very popular in this regard.

bomb calorimeter

Definition of a Calorimeter

Using Calorimeters, we are able to know exactly how many calories we’re consuming when we eat any food product. A calorimeter is used to measure the enthalpy means the heat energy of a reaction.

Calorimeters can vary in quality. Simple calorimeters are used in high school chemistry classrooms, but much more sophisticated calorimeters are used in the industry.

Uses of Bomb Calorimeter

Bomb calorimeters are devices which are useful to compute the heat of combustion of a chemical reaction. Such information collected from a bomb calorimeter during a chemical reaction will tell scientists whether certain food products are safe for use or not. Some popular uses are as follows:

  1. Thermodynamic Studies

Bomb calorimetry is used mainly in the scientific study of thermodynamic processes. It measures the heat of combustion produced in a chemical reaction.

Also, it measures reaction enthalpy and change in enthalpy throughout the reaction. Obviously Bomb calorimeter is very essential to scientific and theoretical thermodynamic studies.

  1. Educational Training

This is another use of bomb calorimeters which is in education training. Calorimetry is being studied in university-level science courses and also in some high school classes.

  1. Fuel Testing

These are used to test the calorific value of solid and liquid fuels, which are traded based on these values. Fuels such as coal and oil must meet the regulations regarding the total calorific value, quality, and purity of the fuel. Bomb calorimetry can also test liquid fuels such as gasoline and kerosene.

  1. Waste and Refuse Disposal

The cement industry uses hazardous waste as an alternative fuel. But the use of hazardous waste as fuel is regulated by the government, by Environmental Protection Agency.

Using Bomb calorimetry we can determine whether hazardous waste fuel meets the regulations or not.

  1. Metabolic Studies

Bomb calorimetry can also determine the calorie content of a product. Using this process one can examine the effects of energy content in food on humans and animals.

These studies are showing implications that extend into nutritional considerations and the effects of diet on the body.

  1. Propellant and Explosive Testing

We use bomb calorimeter to test propellants and explosives to find the product’s heat of detonation.

Relevant Equation for the Bomb Calorimeter

Due to reaction taking place in the calorimeter, the temperature of the water bath changes. It is a fact that in an ideal calorimeter, heat exchange must take place with the water. But, in real life, the materials from the calorimeter itself exchange heat with the system.

We can make corrections for this by considering a heat capacity for the calorimeter also. Since it exchanges all the heat inside the calorimeter, so we can set the total heat to zero.

Here we have three parts of our calorimeter: calorimeter itself, water bath, and chemical reaction. The equation below explains it:

qcal + qwater+qrxn=0

Now, by substituting the equations for the heat of the water and the heat of the calorimeter, the detailed equation:

Ccal ΔTcal + m Cp Δ Twater+ qrxn =0

Here term for qcal has no mass because it assumes that the mass of the calorimeter is constant and therefore we can combine it with Ccal. Also, we can calculate ΔT as

Tf (final temp) – Ti (initial temp).

Cp is the specific heat capacity for water and is 1 cal/g°C.

Thus solve for qrxn :

qrxn = – (Ccal ΔTcal + m Cp ΔTwater)

Solved Question for You

Q: Which of the following statement(s) is/are correct?

  1. Bomb calorimeter can measure high-temperature reactions.
  2. In a bomb calorimeter, the reaction takes place only in the water.
  3. A bomb calorimeter can measure the heat flow of reactions involving gases.
  4. A bomb calorimeter can measure the heat flow of the reaction, equal to the magnitude of the enthalpy change.

Ans: Statements C and D are correct, as these are based on the working of Bomb calorimeter.

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