Explain how a calorimeter works and how you can calculate the heat given off or absorbed by the reaction that is being studied

Question

frostbite · Answer

A calorimeter works by measuring the difference in temperature be when we observe a reaction $A \to B$. The heat given off or absorbed, can be calculated from strict thermodynamics:
The first law of thermodynamics:
$$\Large \Delta U=q+w$$
Here is $\Delta U$ the change in internal energy, $u$ is the heat process and $w$ is the work process. Lets assume we hold the volume constant and no addition work happens. We get that
$$\Large \Delta U=q$$
For the reaction  $A \to B$ the change in internal energy is given by
$$\Large \Delta U=U_{B}(T)-U_{A}(T)$$
Now usually the products with have a higher or lower temperature than the starting point, making the equation above non-useable. We can sort out this by removing the produced heat. If the products got a heat capacity, $C$, we want to remove the heat contribution equal to $C\Delta T$. So if we experimentally find $\Delta T$, and the heat capacity $C$ is known, we can find the wished energy changed as:
$$\Large \Delta U=U _{B}(T)-U _{A}(T)=-C \Delta T$$
This is the basic principle calorimeters work on. It is a bit complex if not familiar with the first law of thermodynamics.

ria23 · Answer

Thank yhu so much for yhur help! ^.^