Calorimetry Worksheet Answer Key

Calorimetry: What is it?

Calorimetry is a technique for determining the enthalpy change of the reaction, as we discussed previously. In other terms, it counts the amount of heat a reaction produces. Direct measurement of the change in heat, however, is not possible. Instead, we must gauge the temperature shift brought on by heat.

Heat is not the same as temperature. An example of energy is heat. It is the culmination of every particle’s energy in a substance. It is measured in joules (J) or kilojoules, like all other forms of energy (kJ). The measurement of energy is temperature, on the other side. It is measured in kelvin (K), degrees Celsius (°C), or degrees Fahrenheit and has to do with the average energy of particles in a substance.

One crucial distinction to make is that while temperature is unrelated to a substance’s particle count, heat is. A substance’s overall energy store grows as its particle count does, which causes the substance’s heat to rise. The temperature, however, may not necessarily vary because of their average energy.

Heat energy always moves from a hot substance to a cold one, or from something that is hot to something that is cold. Energy is transferred to a substance when it is heated. The temperature may rise as a result of this. But it might also result in a state change. But only if the substance maintains its current state.

Calorimetry types

There are several types of calorimetry, including:

• Calorimetry directly
• By-pass calorimetry
• Calorimetry that uses differential scanning

You simply need to be familiar with direct calorimetry for your tests. Unless we specifically state otherwise, the term “calorimetry” in the remainder of this article refers to this. This is what most people mean when they use the term. However, as additional instances of interest, we’ve added the different varieties of calorimetry below.

Calorimetry directly

As the name implies, direct calorimetry detects the heat change caused by a chemical process by taking a direct reading of the temperature change it produces. A calorimeter is used to accomplish this.

A calorimeter is a device that calculates the enthalpy change that occurs during a chemical process.

Water, a thermometer, and a polystyrene cup can be used to create a straightforward calorimeter. Our target reaction produces heat energy, which warms the water. The goal is to minimize heat loss, monitor the water’s temperature change, and utilize this information to determine the reaction’s enthalpy change.

Direct calorimetry in biology mainly refers to monitoring the temperature change of the air around a live thing while it is enclosed in a sealed chamber.

By-pass calorimetry

The phrase “indirect calorimetry” is used in biology. It is a technique for determining how much heat an organism generates by monitoring its oxygen intake, carbon dioxide emission, or nitrogen output.

Calorimetry that uses differential scanning

To raise their temperature, different materials require varying amounts of heat energy. The energy difference required to raise the temperatures of a sample and a reference substance by the same amount is measured using the differential scanning calorimetry technique.

Experiment Using Calorimetry

One sort of calorimeter has already been investigated. It is made comprised of a polystyrene cup that has water or another liquid inside. The water is heated using the heat energy released during a reaction, and the water’s temperature change is gauged. We will now examine how to utilize calorimetry to calculate the enthalpies of reaction, neutralization, and combustion in more detail.

The enthalpy change of a reaction is the enthalpy change that occurs when an equation’s worth of reactants combine to form products under standard conditions and with all species in their usual states.

Under typical circumstances, the enthalpy change of neutralization is the enthalpy change that occurs when an acid and an alkali combine to form one mole of water.

finding the reaction’s enthalpy

You may calculate the enthalpy of reaction using calorimetry for reactions involving the blending of two solutions or the addition of a solid to a solution. This is accomplished by either combining the two solutions or incorporating the solid into the solution, then monitoring the temperature change in the solution. We’ll add a solid to an aqueous solution in this example. This is how to do it:

1. Rinse a measuring cylinder and a polystyrene cup in the solution you’ll be using, then thoroughly dry them.
2. Pour 50 cm3 of the solution into the polystyrene cup after measuring it out. Add a lid on top of the cup and set it inside a beaker.
3. About 2.00g of your solid reactant should be weighed out into a weighing boat.
4. Make a hole in the lid and insert a thermometer. For three minutes, check the solution’s temperature every 30 seconds.
5. Add your solid reactant to your solution rather than taking a temperature reading after the third minute. To determine whether any solid was left behind, reweigh the weighing boat. Then, deduct that amount from the initial weight.
6. For five minutes, or until the temperature is steady, check the solution’s temperature every 30 seconds.

Instead, measure out each solution into a different measuring cylinder and rinse them both in the appropriate solution if you want to combine two watery solutions. Fill the polystyrene cup with the first solution. Every 30 seconds, record the temperatures of the two solutions. Add the second solution to the first at the three-minute mark and keep checking the temperature as described above every 30 seconds.

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the enthalpy change to be found

Now that we know the reaction’s temperature change, we can utilize that information to determine the reaction’s enthalpy change. But we don’t know what temperature it was at the precise instant we introduced the solid and the reaction began. Our first data point is at the 3 minute 30 second mark, but the point of addition is 3 minutes. We must first create a graph of the temperature of the solution against time and extrapolate the temperature back to the point of addition in order to determine the precise temperature rise of the reaction. Sound perplexing? Here’s how to go about it.

calculating the neutralization enthalpy

The process for determining the enthalpy of neutralization is the same as that for determining the enthalpy of reaction. No matter if your two reactants are solids or liquids, you combine them and measure the temperature change over a period of time. In order to determine a maximum temperature, you then draw a graph and extrapolate back to the point of addition. Then, as previously mentioned, you determine the temperature change and perform the enthalpy change calculation.

calculating the combustion enthalpy

We can use calorimetry to determine the enthalpy of combustion for reactions involving combustion. In order to do this, we burn a fuel below a beaker of water, then monitor the water’s temperature change.

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