Question about thermodynamic quantities

In summary, for constant pressure thermodynamic processes, dH=dqp. This implies that only reversible work is possible, resulting in dw=0 if dv is zero. The heat transfer, qv, must also be reversible in this case. However, if the heat transfer is irreversible, the process is not reversible. The same applies for dU=dqv, where the process must be reversible for the relation to hold. The above relations do not necessarily depend on the system being an ideal gas, as they also apply for non-ideal gases. However, in non-ideal gases, du≠dqv in Joule's free expansion. Considering reversibility and the type of gas, there are four possible combinations: ideal gas reversible,
  • #1
kelvin490
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We know that for constant pressure thermodynamic processes, dH=dqp. My question is, does it implies that only reversible work is possible in this processes so that dw=0 because dv is zero? In addition, does qv necessarily be reversible heat transfer in this case? What if the heat transfer is irreversible?

Similar question for dU=dqv, does the process need to be reversible?

Another question is, do the above relations have anything to do with whether or not the system is an ideal gas? I have heard from a lecture that du≠dqv in Joule's free expansion for non-ideal gas. Consider reversibility and whether it's ideal gas there are four combinations of situations (ideal gas reversible,ideal gas irreversible, non-ideal gas reversible, non-ideal gas irreversible). I get confused with how these factors affect the thermodynamic relations.
 
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Is it true that reversible process can only occur in the form of infinitesimal expansion/compression?
 

1. What are the three main thermodynamic quantities?

The three main thermodynamic quantities are energy, entropy, and temperature. These quantities describe the state of a system and how it will behave under different conditions.

2. How do thermodynamic quantities relate to each other?

Energy, entropy, and temperature are related through various thermodynamic laws such as the first and second laws of thermodynamics. These laws describe how energy is conserved and how it flows from one form to another, and how entropy always increases in a closed system.

3. What is the difference between internal energy and enthalpy?

Internal energy is the total energy of a system, including its kinetic and potential energy. Enthalpy, on the other hand, is the sum of internal energy and the product of pressure and volume. It is often used to describe energy changes in chemical reactions.

4. How can thermodynamic quantities be measured?

Thermodynamic quantities can be measured using various instruments such as thermometers, calorimeters, and pressure gauges. These instruments allow us to measure temperature, energy changes, and pressure, which are all important in understanding thermodynamic systems.

5. How are thermodynamic quantities used in practical applications?

Thermodynamic quantities are used in a wide range of practical applications, including power generation, refrigeration, and chemical reactions. They help us understand how energy is converted and transferred, and how systems can be optimized for maximum efficiency.

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