Constant-volume calorimetry | Thermodynamics | AP Chemistry | Khan Academy | Summary and Q&A

TL;DR

Calorimetry measures heat flow and a constant volume calorimeter, also known as a bomb calorimeter, is a type of calorimeter used in this process.

Key Insights

• 🥵 Calorimetry is used to measure heat flow in chemical reactions.
• 💦 Constant volume calorimeters, also known as bomb calorimeters, are used when no work is done.
• 🥵 The heat transferred in a constant volume calorimeter is equal to the change in internal energy.
• 🤗 Constant pressure calorimeters, on the other hand, involve work done by the system.
• 🥵 The heat capacity of a calorimeter can be determined by combusting a substance with a known heat of combustion.
• 🥵 The heat capacity is used to calculate the heat of combustion for another substance.
• 💱 The change in internal energy is often approximately equal to the change in enthalpy.

Transcript

• [Instructor] Calorimetry refers to the measurement of heat flow. And there are many different types of calorimeters. In this case, we're looking at a constant volume calorimeter which is also called a bomb calorimeter. Let's look at how a bomb calorimeter works. First, the sample to be combusted is placed in a container that has some oxygen. And ... Read More

Questions & Answers

Q: What is calorimetry?

Calorimetry is the measurement of heat flow in a system. It involves using calorimeters to measure the transfer of heat during chemical reactions.

Q: How does a constant volume calorimeter work?

In a constant volume calorimeter, a sample is combusted in a container with oxygen, and the heat is transferred to the surrounding water. The temperature increase of the water is measured to determine the heat transferred.

Q: What is the difference between constant volume and constant pressure calorimetry?

In constant volume calorimetry, the walls of the calorimeter are rigid, and no work is done, so the heat transferred is equal to the change in internal energy. In constant pressure calorimetry, work is done as gases expand, and the heat transferred is equal to the change in enthalpy.

Q: How is the heat capacity of a calorimeter determined?

The heat capacity of a calorimeter can be determined by combusting a known amount of a substance with a known heat of combustion and measuring the temperature change of the water in the calorimeter.

Summary & Key Takeaways

• Calorimetry is the measurement of heat flow and can be done using different types of calorimeters.

• In a constant volume calorimeter, a sample to be combusted is placed in a container with oxygen, and the heat from the combustion reaction is transferred to the water in the container.

• The heat transferred in a constant volume calorimeter is equal to the change in internal energy, while in a constant pressure calorimeter, it is equal to the change in enthalpy.