Question

What Is enthalpy and entropy?

Answer 1

Part 1: Enthalpy

1. Enthalpy is defined as the absorption of heat energy when the system changes, or the heat which is emitted out when some change occurs in the system.
2. We can also define enthalpy in terms of entropy and work done.
3. Change in enthalpy of the system is the sum of internal energy with a product of pressure and volume.
4. Enthalpy can be mathematically represented as follows: $∆\mathrm{H}=∆\mathrm{U}+\mathrm{P}∆\mathrm{V}$, where is the$∆\mathrm{H}$ change in enthalpy,$∆\mathrm{U}$ is the change in internal energy, P is the pressure, and is $∆\mathrm{V}$the change in volume.
5. If the change in enthalpy is greater than 0, this signifies that heat is absorbed by the system and hence the process is endothermic in nature.
6. If the change in enthalpy is lesser than 0, this signifies that heat is evolved by the system and hence the process is exothermic in nature.

Part 2: Entropy

1. Entropy is defined as the degree of disordered particles present in a system.
2. Entropy is the ratio of heat exchange over absolute temperature.
3. The actual entropy of the system can not be calculated or determined rather change in entropy can be identified.
4. Thus, mathematically entropy is represented as follows:$∆\mathrm{S}={\left(\frac{∆\mathrm{Q}}{\mathrm{T}}\right)}_{\mathrm{rev}}$, where$∆\mathrm{S}$ is the change in entropy, $∆\mathrm{Q}$is the change in heat, and T is the absolute temperature.