Intermediate Topic 344 of 1102 Thermodynamics & Energetics
Bomb Calorimeter
A constant-volume calorimeter used to measure heat of combustion.
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In-depth explanation of Bomb Calorimeter
A bomb calorimeter is a robust, sealed steel vessel of fixed volume that is filled with oxygen and immersed in a water jacket. A weighed sample is ignited electrically inside the bomb, and the temperature rise of the surrounding water is recorded to determine the heat evolved. Because the volume is constant, the heat measured corresponds to the change in internal energy, q_v equal to delta U, rather than to enthalpy. To obtain the enthalpy change at constant pressure, the relation delta H equals delta U plus delta n times RT is applied, where delta n is the change in moles of gas. Bomb calorimeters are the standard method for determining heats of combustion of fuels and foods.
Going deeper: Bomb Calorimeter
Key ideas: The bomb is rigid, so the heat equals delta U. Calibrate the apparatus with a standard such as benzoic acid, whose heat of combustion is known precisely, to find the calorimeter constant. Then q equals C_cal times delta T, and the molar value is divided by moles of sample. Convert to delta H using delta n of gas.
Common mistakes and connections: Students quote the bomb result directly as delta H, missing the small correction. Another mistake is forgetting the heat from the ignition wire in precise work. The technique ties to calorific value, food energy labels and the first law at constant volume.
Visualization of Bomb Calorimeter
After ignition at constant volume, the jacket temperature rises sharply and levels off. Heat capacity of the calorimeter gives the energy of combustion. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Heats of combustion for fuels such as octane are commonly measured in a bomb calorimeter, with the sample burned in pressurized oxygen.
Frequently asked questions about Bomb Calorimeter
What is Bomb Calorimeter?
A constant-volume calorimeter used to measure heat of combustion.
Is Bomb Calorimeter a beginner, intermediate or advanced topic?
Bomb Calorimeter is a intermediate topic in Thermodynamics & Energetics. It builds on the vocabulary of beginner topics in this area.
What should I learn before Bomb Calorimeter?
Study these earlier topics in Thermodynamics & Energetics first: Specific Heat Capacity, Molar Heat Capacity, Calorimetry.
What comes after Bomb Calorimeter?
The next topics in Thermodynamics & Energetics are Coffee-Cup Calorimeter and Thermochemical Equation.
Can I practise Bomb Calorimeter with quizzes?
Yes. The interactive lesson includes a self-check question on Bomb Calorimeter, and the Thermodynamics & Energetics quiz draws on every topic in this area.
Where Bomb Calorimeter fits in Thermodynamics & Energetics
Bomb Calorimeter is topic 16 of 91 in Thermodynamics & Energetics.