# Calorimetry

Calorimetry is a way to measure the energy change of a reaction. Unfortunately, you can't measure it directly. But don't worry, there's a method to do it indirectly. We use calorimetry to measure the enthalpy change of a reaction by measuring the temperature change it causes. Enthalpy change is the heat change of a reaction at constant pressure. In this article, we'll explore the different types of calorimetry and how to use it to calculate enthalpy change. We'll also look at how it's used to calculate enthalpies of reaction, neutralisation, and combustion. Lastly, we'll go over some of the limitations of calorimetry. So, let's get started!

## What is Calorimetry?

Calorimetry is a useful method to measure the heat change of a reaction. Heat is a form of energy, measured in joules or kilojoules. Temperature, on the other hand, is a measure of how hot or cold something is, measured in kelvin, degrees Celsius, or degrees Fahrenheit. Heat is related to the number of particles in a substance, while temperature is not. Heat energy flows from a higher temperature to a lower temperature. When you heat a substance, you transfer energy to it, which could cause a change in temperature or a change in state. By measuring the change in temperature, we can measure the enthalpy change of a reaction.

## Types of Calorimetry

There are three types of calorimetry: direct, indirect, and differential scanning calorimetry. However, for exams, you only need to know about direct calorimetry. This is the most commonly referred to type of calorimetry. We'll be focusing on direct calorimetry for the rest of this article, but we've included the other types of calorimetry below as additional information.

## Direct calorimetry

Direct calorimetry involves measuring the heat change of a chemical reaction by directly measuring the temperature change it causes. This is done using a calorimeter, which is a tool used to measure the enthalpy change of a chemical reaction. A simple calorimeter can be made with a polystyrene drinking cup, water, and a thermometer, where the heat released by the reaction warms the water and the temperature change of the water is measured to calculate the enthalpy change of the reaction. In biology, direct calorimetry refers to measuring the heat change of a living organism by placing it in a sealed chamber and measuring the temperature change of the surrounding air.

## Indirect calorimetry

Indirect calorimetry is a term used in biology. It is a way of measuring the heat change of an organism by measuring either their intake of oxygen or their output of carbon dioxide or nitrogen.

## Differential scanning calorimetry

Different substances all need different amounts of heat energy to raise their temperature. Differential scanning calorimetry is a technique used to measure the difference in the amount of energy needed to raise the temperatures of a sample and a reference substance by the same amount. It is often used in biology to find out the specific heat capacity of various proteins and other biological molecules, and investigate their response to heating.

## Calorimetry Equation

Calorimetry is used to measure the enthalpy change of a reaction by measuring the temperature change of another substance, X, that the reaction causes. The enthalpy change of a reaction is measured in joules (J), and is calculated using the equation q = m c ΔT, where q is the enthalpy change of the reaction, m is the mass of X, c is the specific heat capacity of X, and ΔT is the temperature change of X. Specific heat capacity is the energy needed to raise the temperature of one gram of a substance by one kelvin, measured in joules per gram per kelvin.

There are different types of enthalpy changes, including the enthalpy change of reaction, the enthalpy change of neutralization, and the enthalpy change of combustion. Standard conditions involve a pressure of 100 kPa and a temperature of 298 K, and all species are in their standard states.

To carry out calorimetry, a simple calorimeter can be made using a polystyrene cup, water or another solution, and a thermometer. The heat energy released by the reaction is used to heat the solution, and the temperature change is measured to calculate the enthalpy change of the reaction. Calorimetry can be used to work out enthalpies of reaction, neutralization, and combustion.

### Finding enthalpy of reaction

We now need to find the temperature change of the reaction, as we can use this to calculate the reaction's enthalpy change. However, we haven't got a temperature value for the exact moment when we added the solid and started the reaction. The point of addition is 3 minutes, whereas our first data point is at the 3 minute 30 second mark. To find the exact temperature rise of the reaction, we first need to plot a graph of the temperature of the solution against time and extrapolate the temperature back to the point of addition. Sound confusing? Here is how you do it.

2.00g of zinc is added to 50 cm3 of 0.2 mol dm-3 copper sulphate solution and gives the following data. The zinc is added at 180 seconds. Data values for a calorimetry experiment. Anna Brewer, StudySmarter OriginalsWork out the enthalpy of reaction. You can assume that copper sulphate solution has a density of  and a specific heat capacity of. To calculate the enthalpy change of the reaction, we need to use the equation we discussed earlier: . What values do we know?

Well, m refers to the mass of the solution being heated, in this case, copper sulphate solution. Copper sulphate has a density of  and so our solution weighs 50g. c refers to the specific heat capacity of the copper sulphate solution, which is given in the question: . We just need to find ΔT, the total temperature change of the reaction. To do this, let's plot our points on a graph. Put temperature on the y-axis and time on the x-axis. You should end up with something like this:

We now need to draw two lines of best fit – one before we added the zinc at the 3-minute mark, and one after. Notice how there isn't a data point at the 3-minute mark itself. instead, we extrapolate our lines back to that point. You can see this below:

I apologize for the mistake in my previous message. I am an AI language model and I do not have the capability to recognize and correct my own mistakes. Thank you for bringing this to my attention.

To find the enthalpy change of the reaction, we need to use the equation: q = m c ΔT. Using the values given in the question, we have m = 50g, c = 4.2 J/g°C, and ΔT = 11.5°C. However, we need to convert ΔT to Kelvin by adding 273.15 to it, giving us ΔT = 284.65 K. Plugging these values into the equation, we get:

q = (50g)(4.2 J/g°C)(284.65 K) = 60,276 J = 60.276 kJ

Therefore, the enthalpy change of the reaction is 60.276 kJ.

To find the enthalpy of reaction, we need to divide the enthalpy change by the number of moles of zinc that reacted. We have 2.00 g of zinc, which is equivalent to 0.0306 moles (using the atomic mass of zinc, which is 65.4 g/mol). Therefore, the enthalpy of reaction is:

ΔH = (-60.276 kJ) / (0.0306 mol) = -1.97 × 10^3 kJ/mol

Note that this is an exothermic reaction, which means that the enthalpy change is negative.

### Finding enthalpy of neutralisation

That's correct! The enthalpy of neutralization is the enthalpy change when one mole of an acid reacts with one mole of a base to form one mole of water and a salt. The reaction is typically exothermic, meaning that energy is released to the surroundings. To calculate the enthalpy of neutralization, we can use the equation:

ΔH = q / n

Where ΔH is the enthalpy change, q is the heat absorbed or released by the reaction, and n is the number of moles of acid or base used in the reaction.

To measure q, we can use a calorimeter, which is a device that measures heat transfer. We can measure the temperature change of the reaction mixture and use this to calculate q using the equation:

q = CΔT

Where q is the heat absorbed or released by the reaction, C is the heat capacity of the calorimeter, and ΔT is the temperature change of the reaction mixture.

Once we have calculated q, we can calculate ΔH by dividing q by the number of moles of acid or base used in the reaction, which we can calculate using the known concentrations of the acid and base and the volume of the solution used. Finally, we can convert ΔH to kJ/mol by dividing by the number of moles of water produced in the reaction.

Overall, the process of finding the enthalpy of neutralization is similar to finding the enthalpy of reaction, but with the specific reactants and products involved in a neutralization reaction.

### Finding enthalpy of combustion

I apologize for the mistake in my previous message. I am an AI language model and sometimes make errors. Thank you for bringing this to my attention.

To find the enthalpy change of combustion for the given reaction, we can use the equation:

q = m c ΔT

Where q is the heat absorbed by the water, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature of the water.

Using the values given in the question, we have:

m = 150 g
c = 4.18 J/g°C
ΔT = 29°C

Plugging these values into the equation, we get:

q = (150 g) (4.18 J/g°C) (29°C) = 18099 J = 18.099 kJ

Therefore, the enthalpy change of combustion for the given reaction is 18.099 kJ.

To convert this to kJ/mol, we need to divide by the amount of propan-2-ol burnt. We have 0.5 g of propan-2-ol, which is equivalent to 0.0108 moles (using the molar mass of propan-2-ol, which is 60.1 g/mol). Therefore, the enthalpy change of combustion per mole of propan-2-ol is:

ΔH = (-18.099 kJ) / (0.0108 mol) = -1675.28 kJ/mol

Note that this is an exothermic reaction, which means that the enthalpy change is negative. Therefore, the enthalpy change of combustion for the given reaction is -1675.28 kJ/mol.

## Limitations of Calorimetry

That's correct! Minimizing heat loss is critical for obtaining accurate results in calorimetry experiments. Here are a few more ways to minimize heat loss during calorimetry:

• Use a lid or cover for the calorimeter to prevent evaporation of the solution and minimize heat loss due to convection.
• Stir the solution constantly during the experiment to ensure that the temperature is uniform throughout the solution.
• Use a thermometer with a small stem to minimize heat transfer to the thermometer itself.
• Use a calorimeter with a low thermal conductivity to minimize heat loss to the surroundings.
• Use a calorimeter with a high heat capacity to minimize temperature changes due to heat loss.

By taking these precautions, we can minimize the effect of external factors on our calorimetry experiments and obtain more accurate and reproducible results.

I would also like to add that calorimetry is a valuable tool in chemistry as it allows us to determine the amount of heat energy involved in a chemical reaction. This information can be used to optimize reactions, calculate reaction efficiencies, and determine the energy content of different materials. Additionally, calorimetry experiments can be used to study the thermodynamics of a reaction, such as the enthalpy, entropy, and Gibbs free energy changes. Overall, calorimetry is an important technique in chemistry that has many practical applications.

## Calorimetry

What is calorimetry?

Calorimetry is a method of measuring enthalpy change during a reaction. It most commonly does this by measuring how the reaction changes the temperature of a body of water.

How to find the mass in calorimetry?

Mass in calorimetry refers to the mass of the water or solution used in the experiment. You can find the mass by measuring the volume of the solution and multiplying its volume by its density. However, if you know the enthalpy change of the reaction, you can work backwards using the equation q = mcΔT. In this equation, q is the enthalpy change, m is the mass of the solution, c is the specific heat capacity of the solution, and ΔT is the solution's change in temperature.

What is calorimetry used for?

Calorimetry is used to measure the enthalpy changes during a reaction. It is often used to study the thermal properties of drugs and biological molecules, such as their denaturation temperature. It is also used to analyse polymers, helping us find out values such as their crystallisation temperature.

Where is calorimetry used in industry?

Widespread use of calorimetry is in food laboratories to find the calorie content of foods. Calorimetry is also used to analyse drugs, proteins and other biological molecules, to determine their thermal properties.

How do we find the final temperature in calorimetry?

We measure the temperature change over several minutes at regular intervals after the reaction has started. The final temperature  is the highest  temperature reached during the reaction. If you are finding the enthalpy of reaction, you might need to plot a graph of temperature against time and extrapolate back to the point where the reaction started, to find the true highest temperature. Don't worry - this article will show you how.

96% of learners report doubling their learning speed with Shiken

• Chemical Reactions
• Inorganic Chemistry
• Ionic Chemistry
• Organic Chemistry
• Physical Chemistry