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An Introduction to Bomb Calorimeter

Last updated date: 14th Mar 2023
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To test the calorific value of liquid and solid fuels that are traded based on the value, we tend to use a bomb calorimetry. Fuels like coal and oil must meet rules specifying the overall calorific value to make sure the standard and purity of the fuel. The heat that's measured is stated as the change of internal energy (E). The heat changes of a reaction are often monitored in chemistry at a fixed pressure or volume. How to use a bomb calorimeter, construction of bomb calorimeter, how does a colorimeter work, bomb calorimetery calculations and many more concepts will be discussed in this article.

What is Bomb Calorimeter?

The calorimeter used to verify the energy change throughout a reaction is known as a bomb calorimeter. The calorimeter of Berthelot is the origin of the modern bomb calorimeter.

Bomb calorimeters should resist the high pressure inside the calorimeter, whereas measuring the response. The fuel is ignited using electrical energy; once the fuel burns, it heats up the surrounding air that expands and exits through a tube leading out of the calorimeter. Once air escapes through the copper tube, it heats the water outside the tube also. The calorie content of the fuel is also calculated using the temperature change within the water.

To test the calorific value of solids and liquid fuels bomb calorimeters are used. If the heat capability of the calorimeter is known, we are able to determine the change in heat by noting the temperature. Fuel like coal and oil must meet rules specifying the entire calorific value.

Construction of Bomb Calorimeter

Bomb Calorimeter

Bomb Calorimeter

Bomb calorimetery calculations are performed as follows:

The sample, oxygen, the stainless-steel bomb, and water compose the bomb calorimeter's main parts.

The wall stops heat from escaping from the calorimeter into the rest of the cosmos, i.e.

q calorimeter = 0.

The combustion process happens at a fixed volume and there's no work because the bomb is constructed of stainless-steel.

Wc calorimeter = - p dV = 0

Thus, the change in internal energy, dU, for the calorimeter is zero.

dU calorimeter = q calorimeter + w calorimeter = 0

The thermodynamic interpretation of this equation is that the calorimeter is isolated from the remainder of the universe.

Working of Bomb Calorimeter

The bomb is used to determine the hot values of liquid and solid fuels. It consists of a robust steel shell referred to as a bomb. The calorimeter consists of steel that has excellent corrosion resistance and may sustain high pressures. Within the calorimeter, a robust cylindrical bomb is used to cause combustion. Just at the apex of the bomb, there ar 2 values. One provides O to a bomb, whereas the other emits fumes.

The bomb is placed within a copper vessel that contains water. Inside the calorimeter, there's a stirring device for agitating the water. The calorimeter containing the bomb is placed in another container that acts as a heat insulator. Using the thermometer the temperature of water in the calorimeter is measured.

The calorimeter is additionally equipped with a water and air jacket to decrease light losses. Through the lid of the calorimeter, a stirrer keeps the temperature of the water consistent, and a thermometer with a temp precision of 0.001 degree C is installed. The surroundings are completely different and also the calorimeter absorbs the heat generated by the fuel during burning.

Uses of Bomb Calorimeter

  • Bomb calorimeter set up is used primarily in the scientific study of thermodynamical processes. It measures the heat of combustion produced in a chemical process. Also, it measures changes in physical property throughout the reaction.

  • They are used to test the hot value of liquid and solid fuels that are traded based on the calorific values. Fuels like coal and oil should meet the rules regarding the overall calorific value to make sure the standard and purity of the fuel. Bomb calorimetry may test liquid fuels like gasolene and lamp oil.

  • It may determine if the industries are using unsafe waste as an alternate fuel by generating the values.

  • It can also make sure the calorie content of a product, so we are able to examine the content in food on humans, and also thereby extend into nutritionary concerns and the effect of diet on the body.

  • We can also find the heat of detonation of test propellants and explosives.

Key Features

  • A bomb calorimeter consists of small sample cup, oxygen, a stainless-steel bomb, water, a stirrer, a thermometer, a dewar or an insulating bottle and an ignition circuit.

  • The reaction takes place only in water after we talk about bomb calorimeter.

  • It can measure heat flow of the reaction, which can be equal to magnitude of enthalpy change.

  • When measuring heat prospective or the basic heat of a substance, many students use calorimeters. A calorimeter is employed to calculate the overall heat energy and subsequently to measure the precise heat of a substance or other heat related data.

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FAQs on Bomb Calorimeter

1. What is the principle of  bomb calorimeter?

Combustion calorimeters calculate the heat that a flammable solid-liquid material emits. This is often achieved by measuring into a crucible a precise amount of the sample material, putting the crucible within a “bomb” (a capsulated metal container referred to as a pipe), filling the O pipe and igniting the material. The modern bomb calorimeter is formed of corrosion-resisting steel within the combination bomb calorimeter. The bomb calorimeter is an instrument used to measure the heat of a reaction at a fixed value of volume and also the measured heat is termed the change of internal energy. 

2. What are the necessary features of a calorimeter?

A calorimeter could be a device that is used for measuring the heat of chemical reactions or physical changes also as heat capacity. The most common varieties of calorimeters are differential scanning calorimetry, titration calorimetry, isothermal microcalorimetry, and accelerated rate calorimetry. A standard calorimeter usually consists of a thermometer. The calorimeter could be a small container made from a metal, like gold or copper, with good thermal conduction. It has a temperature detector that continuously has to be at exactly the same temperature as the calorimeter and its contents.

3. How can we calculate heat using a bomb calorimeter?

Heat given by the combustion of fuse wire + Heat given by the combustion of coal = Heat taken by the water and calorimeter.

If the heat capacity of the calorimeter is known, the heat change throughout a reaction is determined by noting the change within the temperature in the process.

The heat q = Cv(Tf –Ti); where q is the quantity of heat according to the change in temperature measured in joules. Cv is the heat capacity of the calorimeter, Ti is the initial temperature and Tf is the final temperature.