How Do We Calculate Entropy Change for an Ideal Gas?

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In summary, the question is asking for the entropy change of a system involving n moles of an ideal gas. The first law of thermodynamics equation, ΔS=qrev/T=(ΔU-w)/T, is used to solve the problem, with a negative sign. The given answer is nCvln(T2/T1)+nRln(V2/V1), which involves the change in temperature and volume. The origin of this answer is unclear, as it does not specify if the process is isothermal or not.
  • #1
mooncrater
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Homework Statement


The question says:
In a process involving n moles of an ideal gas , what is the entropy change of the system ?

Homework Equations


ΔS=qrev/T=(ΔU-w)/T
(I have used the chemistry's equation of 1st law of thermodynamics which has the -ve sign)

The Attempt at a Solution


The answer given is that:
nCvln(T2/T1)+nRln(V2/V1).
I don't know how they are giving this answer. The second term seems to be originated from work done in isothermal conditions . But its not given that the process is an isothermal one. And the first term ...huh..I don't know where it came from. So what is the origin of this answer?
 
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  • #2
mooncrater said:
In a process

What process?
 
  • #3
Borek said:
What process?
There is nothing else given in the question.
 

FAQ: How Do We Calculate Entropy Change for an Ideal Gas?

1. What is entropy and why is it important in science?

Entropy is a measure of the disorder or randomness in a system. It is important in science because it helps us understand how energy flows and changes within a system, and it is a fundamental concept in thermodynamics and statistical mechanics.

2. How do we represent entropy in scientific models?

Entropy is typically represented by the symbol "S" and is measured in units of joules per Kelvin (J/K) in the International System of Units (SI). In scientific models, entropy is often used to describe the amount of energy that is unavailable to do work in a closed system.

3. Is there a difference between entropy and enthalpy?

Yes, there is a difference between entropy and enthalpy. Entropy is a measure of disorder, while enthalpy is a measure of the total energy in a system. Entropy is also related to the probability of a system's microstates, while enthalpy is related to the potential energy of a system.

4. What are some real-world examples of entropy?

Some real-world examples of entropy include: the melting of ice cubes, the mixing of hot and cold water, the rusting of metal, and the diffusion of perfume in a room. In all of these cases, there is an increase in disorder or randomness in the system, resulting in an increase in entropy.

5. Can entropy be decreased in a closed system?

No, the Second Law of Thermodynamics states that the total entropy of a closed system will always increase or remain constant. While local decreases in entropy are possible, they must be offset by larger increases in entropy in other parts of the system.

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