What Is the Difference Between Bomb and Coffee Cup Calorimeters?

TL;DR

The key difference is that coffee cup calorimeters measure energy changes at constant pressure, while bomb calorimeters measure at constant volume. To calculate the energy of combustion per mole, use the heat capacity of the calorimeter multiplied by the temperature change, and then divide by the number of moles of the substance involved.

Transcript

in this video we're going to talk about how to solve this bomb calorimeter problem but before we go into it i want to highlight the difference between the coffee cup calorimeter and the bomb calorimeter so in the coffee cup calorimeter we're basically going to use a cup ideally made up of styrofoam because styrofoam is a good thermal insulator so w... Read More

Key Insights

• 💘 Coffee cup calorimeters measure constant pressure, while bomb calorimeters measure constant volume.
• 💘 Enthalpy is the energy transferred at constant pressure, and enthalpy change can be calculated using a coffee cup calorimeter.
• 🔇 Bomb calorimeters have a combustion chamber and measure energy released by combustion at constant volume.
• 🥵 The energy of combustion per mole can be calculated using the heat capacity of the calorimeter and the change in temperature.
• 🥵 The heat capacity is used to calculate the energy absorbed by the calorimeter, indicating an endothermic process.
• 🟰 Q of the reaction is equal to the negative Q of the calorimeter in an exothermic process.
• 💆 Molar mass is calculated to convert grams to moles.
• 🗂️ The energy of combustion per mole is obtained by dividing the energy in kilojoules by the number of moles.

Questions & Answers

Q: What is the main difference between coffee cup and bomb calorimeters?

Coffee cup calorimeters measure energy change at constant pressure, while bomb calorimeters measure energy at constant volume.

Q: Why is it important to measure enthalpy at constant pressure?

Enthalpy is the energy transferred at constant pressure, so measuring at constant pressure ensures accurate calculations.

Q: How is the energy of combustion per mole calculated using a bomb calorimeter?

The heat capacity of the calorimeter and the change in temperature are used in the equation q = CΔT to calculate the energy of combustion.

Q: What is the purpose of the combustion chamber in a bomb calorimeter?

The combustion chamber holds the sample and allows it to release thermal energy into the surrounding water, which measures the temperature change.

Summary & Key Takeaways

• Coffee cup calorimeters use a sealed cup with water and a thermometer to measure the energy change at constant pressure.

• Bomb calorimeters have a separate combustion chamber, and measure energy at constant volume.

• To calculate the energy of combustion per mole, the heat capacity of the calorimeter and the change in temperature are used.