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A calorimeter is a device that measures the amount of heat that is produced by a chemical process or a physical change. Calorimetry is the term for the process of measuring heat. A basic calorimeter consists of a solid container filled with water above a combustion chamber, with a thermometer used to track the temperature change. There are, however, a variety of more complicated calorimeters.
The core principle is that the heat emitted by the combustion chamber causes a quantifiable increase in the temperatures of the water. When compounds A and B react, the temperature change can compute the enthalpy change per mole of substance A.
Cv and Constant Pressure calorimetry are two of the most regularly utilised calorimetry.
Calorimetry is a technique for measuring heat and determining the heat of a reaction through tests. A coffee-cup calorimeter is commonly employed since it is less complicated than a bomb calorimeter (constant pressure calorimetry). Yet, Cv calorimetry or bomb calorimetry is suitable for measuring the heat evolved in a combustion reaction. A Cv calorimeter is more accurate than a coffee-cup calorimeter. Still, it’s more difficult to use since it requires a well-built reaction container that can withstand high-pressure changes, which are typical in chemical reactions.
Constant volume calorimetry, often known as Cv calorimetry, is a type of calorimetry technique for calculating a reaction’s heat of combustion.
Constant volume calorimetry
Bomb calorimetry is a technique for determining the amount of heat absorbed or released by a reaction, and it is commonly used to determine the calorie content of food.
A bomb calorimeter is a form of Cv calorimeter used to measure the heat of combustion of a specific reaction. If we wanted to know how hot a sushi roll is, we’d look at how many calories it has. To accomplish this, we would place the sushi roll in a “bomb” container, seal it, and then submerge it in the water within the calorimeter. Then we’d remove all of the air from the bomb before injecting pure oxygen gas (O2). Following the addition of oxygen, the sample would be ignited by a fuse, causing it to combust, releasing carbon dioxide, gaseous water, and heat. As a result, bomb calorimeters are engineered to survive the high pressures generated by the gaseous products produced during these combustion processes.
The heat produced in the reaction passes to the water and the calorimeter once the specimen is combusted. A thermometer is used to detect the change in water temperature. The heat acquired by the water and the calorimeter will be equal to the total heat given out in the reaction:
Qrxn = −Qcal
Keep in mind that the heat absorbed by the calorimeter includes both the heat gained by the water and the heat gained by the calorimeter. This can be stated in the following way:
Qcal = mwaterCwaterΔT + CcalΔT
where C water signifies the water’s specific heat capacity and Ccal denotes the calorimeter’s heat capacity (usually in calC). As a result, the calorimeter must be calibrated when doing bomb Cv calorimetry studies to estimate Ccal.
There is no pressure-volume work in a bomb calorimeter because the volume is constant. As a result,
U = qV is obtained.
Where U signifies the change in internal energy of the reaction and qV represents the heat absorbed or emitted by the reaction evaluated under constant volume conditions.
Constant Pressure calorimetry
The constant pressure calorimetry is used to detect changes in the enthalpy of the reaction in liquid solutions at a constant pressure.
The coffee-cup calorimeter, consisting of two nested Styrofoam cups and a lid with two holes for inserting the stirring rod and thermometer, is one of the simplest forms of constant pressure calorimetry.
A specified amount of the liquid, usually water, is placed in the inner cup to absorb the heat from the reaction.
It is assumed that the outer cup is entirely adiabatic, meaning that it will absorb no heat.
As a result, the outer cup is the ideal insulator.
The heat capacity of an unknown substance can be calculated using data acquired during a constant-pressure calorimetry experiment. We already know the relationship between heat (Q), specific heat capacity (C), and temperature change (T):
Q = mCΔT
Working of Calorimeter
A calorimeter is a device that measures how much heat a substance gains or loses. It comprises a vessel made of heat- and electricity-conducting metals such as copper or aluminium. The metallic vessel is housed in an insulating jacket to minimise heat loss to the environment. It has two rips in it. For the working of the calorimeter, a thermometer is put through one hole to measure the temperature of the contents.
To mix the contents of the vessel, a stirrer is placed through another hole. A current is passed through the heating element, which heats the liquid in the jar. We can evaluate the heat capacity of the liquid in the container with this equipment.
Conclusion
A calorimeter is used to measure the warmth of chemical reactions or physical changes.
The reaction’s heat capacity and enthalpy change.
Q = Cv(Tf−Ti)
A type of Cv calorimeter that includes a small cup to hold the sample, oxygen, a chrome steel bomb, water, a stirrer, a thermometer, a Dewar or thermal insulation canister (to keep the calorimeter’s heat from escaping into the environment), and an ignition circuit connected to the bomb, is known as Bomb Calorimeter. The reaction will occur with no volume change if the explosive is made of chromium steel.
