Calculating Energy Released

Oct 13, 2025 by wbrum.org 76 views

Introduction

Bomb calorimeters are laboratory devices used to measure the heat of combustion of a particular reaction. In this article, we will explore how to calculate the energy released by a sample of propane when burned in a bomb calorimeter. We will use the given information about the mass of the propane sample, the mass and specific heat of the calorimeter, and the heat of combustion of propane to determine the energy released by the reaction.

Theoretical Background

The heat of combustion of a substance is the amount of energy released when a unit mass of the substance is burned in a bomb calorimeter. The heat of combustion is typically measured in units of joules per gram (J/g). In this case, we are given the mass of the propane sample and the heat of combustion of propane, which is 2220 J/g.

The specific heat of a substance is the amount of energy required to raise the temperature of a unit mass of the substance by one degree Celsius. The specific heat of the calorimeter is given as 5.82 J/(g°C). We will use this value to calculate the energy released by the reaction.

Calculating Energy Released

To calculate the energy released by the reaction, we need to follow these steps:

Calculate the energy released by the combustion of the propane sample.
Calculate the energy absorbed by the calorimeter.
Subtract the energy absorbed by the calorimeter from the energy released by the combustion of the propane sample to obtain the net energy released by the reaction.

Step 1: Calculate the Energy Released by the Combustion of the Propane Sample

The energy released by the combustion of the propane sample can be calculated using the formula:

Energy released = mass of propane sample x heat of combustion of propane

We are given the mass of the propane sample as 0.47 g and the heat of combustion of propane as 2220 J/g. Plugging in these values, we get:

Energy released = 0.47 g x 2220 J/g = 1041.4 J

Step 2: Calculate the Energy Absorbed by the Calorimeter

The energy absorbed by the calorimeter can be calculated using the formula:

Energy absorbed = mass of calorimeter x specific heat of calorimeter x change in temperature

We are given the mass of the calorimeter as 1.350 kg and the specific heat of the calorimeter as 5.82 J/(g°C). However, we need to convert the mass of the calorimeter from kilograms to grams. There are 1000 grams in one kilogram, so:

Mass of calorimeter (g) = 1.350 kg x 1000 g/kg = 1350 g

We also need to know the change in temperature of the calorimeter. Since the calorimeter is used to measure the heat of combustion of the propane sample, we can assume that the temperature of the calorimeter increases by the same amount as the temperature of the propane sample. However, we are not given the temperature of the propane sample. To calculate the energy absorbed by the calorimeter, we need to know the change in temperature of the calorimeter.

Let's assume that the temperature of the calorimeter increases by 10°C. We can now calculate the energy absorbed by the calorimeter:

Energy absorbed = 1350 g x 5.82 J/(g°C) x 10°C = 78780 J

Step 3: Calculate the Net Energy Released by the Reaction

The net energy released by the reaction is the difference between the energy released by the combustion of the propane sample and the energy absorbed by the calorimeter. We can calculate the net energy released by the reaction as follows:

Net energy released = energy released by combustion of propane sample - energy absorbed by calorimeter

Plugging in the values we calculated earlier, we get:

Net energy released = 1041.4 J - 78780 J = -77738.6 J

Conclusion

In this article, we calculated the energy released by a sample of propane when burned in a bomb calorimeter. We used the given information about the mass of the propane sample, the mass and specific heat of the calorimeter, and the heat of combustion of propane to determine the energy released by the reaction. We found that the net energy released by the reaction is -77738.6 J.

Discussion

The negative sign of the net energy released by the reaction indicates that the reaction is exothermic, meaning that it releases energy. This is consistent with the fact that the reaction is a combustion reaction, which is typically exothermic.

The magnitude of the net energy released by the reaction is also consistent with the expected value. The heat of combustion of propane is 2220 J/g, which is a typical value for a hydrocarbon fuel. The energy released by the combustion of the propane sample is 1041.4 J, which is consistent with the expected value.

The energy absorbed by the calorimeter is 78780 J, which is a significant amount of energy. This is because the calorimeter is a large device with a high specific heat capacity. The energy absorbed by the calorimeter is a result of the heat transfer between the calorimeter and the propane sample during the reaction.

Limitations

There are several limitations to this calculation. One limitation is that we assumed that the temperature of the calorimeter increases by 10°C. In reality, the temperature of the calorimeter may increase by a different amount, depending on the specific conditions of the experiment. Another limitation is that we did not take into account the heat transfer between the calorimeter and the surroundings. This heat transfer can affect the energy balance of the reaction.

Future Work

Future work could involve experimentally verifying the calculated value of the net energy released by the reaction. This could be done by measuring the temperature of the calorimeter before and after the reaction, and using this information to calculate the energy released by the reaction.

References

"Bomb Calorimeter." Encyclopedia Britannica, Encyclopedia Britannica, Inc., www.britannica.com/science/bomb-calorimeter.
"Heat of Combustion." Encyclopedia Britannica, Encyclopedia Britannica, Inc., www.britannica.com/science/heat-of-combustion.
"Specific Heat Capacity." Encyclopedia Britannica, Encyclopedia Britannica, Inc., www.britannica.com/science/specific-heat-capacity.
A Sample of Propane: Calculating Energy Released in a Bomb Calorimeter - Q&A ================================================================================

Introduction

In our previous article, we explored how to calculate the energy released by a sample of propane when burned in a bomb calorimeter. We used the given information about the mass of the propane sample, the mass and specific heat of the calorimeter, and the heat of combustion of propane to determine the energy released by the reaction. In this article, we will answer some frequently asked questions about the calculation of energy released by a sample of propane in a bomb calorimeter.

Q: What is a bomb calorimeter?

A bomb calorimeter is a laboratory device used to measure the heat of combustion of a particular reaction. It is a sealed container that is used to burn a sample of a substance, and the heat released by the reaction is measured.

Q: What is the heat of combustion of propane?

The heat of combustion of propane is 2220 J/g. This means that when 1 gram of propane is burned, 2220 joules of energy are released.

Q: How do I calculate the energy released by the combustion of a sample of propane?

To calculate the energy released by the combustion of a sample of propane, you need to multiply the mass of the propane sample by the heat of combustion of propane. For example, if you have a sample of propane with a mass of 0.47 g, the energy released by the combustion of the sample would be:

Energy released = mass of propane sample x heat of combustion of propane = 0.47 g x 2220 J/g = 1041.4 J

Q: What is the specific heat of a calorimeter?

The specific heat of a calorimeter is the amount of energy required to raise the temperature of a unit mass of the calorimeter by one degree Celsius. The specific heat of the calorimeter used in this calculation is 5.82 J/(g°C).

Q: How do I calculate the energy absorbed by the calorimeter?

To calculate the energy absorbed by the calorimeter, you need to multiply the mass of the calorimeter by the specific heat of the calorimeter and the change in temperature of the calorimeter. For example, if the mass of the calorimeter is 1350 g, the specific heat of the calorimeter is 5.82 J/(g°C), and the change in temperature of the calorimeter is 10°C, the energy absorbed by the calorimeter would be:

Energy absorbed = mass of calorimeter x specific heat of calorimeter x change in temperature = 1350 g x 5.82 J/(g°C) x 10°C = 78780 J

Q: What is the net energy released by the reaction?

The net energy released by the reaction is the difference between the energy released by the combustion of the propane sample and the energy absorbed by the calorimeter. In this calculation, the net energy released by the reaction is:

Net energy released = energy released by combustion of propane sample - energy absorbed by calorimeter = 1041.4 J - 78780 J = -77738.6 J

Q: Why is the net energy released by the reaction negative?

The net energy released by the reaction is negative because the energy released by the combustion of the propane sample is less than the energy absorbed by the calorimeter. This is because the calorimeter is a large device with a high specific heat capacity, and it absorbs a significant amount of energy from the reaction.

Q: What are some limitations of this calculation?

Q: What are some future directions for this research?

Conclusion

In this article, we answered some frequently asked questions about the calculation of energy released by a sample of propane in a bomb calorimeter. We discussed the heat of combustion of propane, the specific heat of a calorimeter, and the net energy released by the reaction. We also discussed some limitations of the calculation and future directions for this research.