Entropy of gas at constant pressure and volume

In summary, the conversation is about a homework problem involving finding the overall change in entropy of 1m^3 of air that is heated and then cooled at constant pressure and volume. The student is struggling to find the correct answer and is asking for help. They have found P2 to be 911kPa but are unsure of the next steps. The other person advises them to use the correct equation for the first process and to be careful with the values for temperature and pressure.
  • #1
ricof
14
0

Homework Statement



1m^3 of air is heated reversibly at constant pressure from 288K to 573K. Then it is cooled reversibly at constant volume back to the initial T. Initial P is 103kPa Calculate overall change in entropy.
Cp=1.02
Cv=0.702

Homework Equations



dS=Cp x ln(T2/T1)-R x ln(P2/P1)


The Attempt at a Solution



I have found P2 to be 911kPa but when I put all the data into the above equation I end up with the wrong answer (0.076kJ/K). Please help!

I have found
 
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  • #2
tell me how u got 911kPa..
its wrong from thr only...
 
  • #3
I used T2/T1 = (P2/P2)^(n-1/n)

and n = Cp/Cv
 
  • #4
for 1st proces which is isobaric...
V1/T1=V3/T3... V1= 1m^3 so one can find V3...3 is the intermediate stage
and then for isochoric process...
P3/T3=P2/T2...
n bcoz T2= T1=288 and P3=P1...
n T3=573
so jus find value n den see...
u r goin in wrong direction...dats actually for adiabatic processes
 

FAQ: Entropy of gas at constant pressure and volume

What is entropy of gas at constant pressure and volume?

The entropy of a gas at constant pressure and volume is a measure of the disorder or randomness of the molecules in the gas. It is a thermodynamic property that describes the distribution of energy within a system.

How is entropy of gas at constant pressure and volume related to the Second Law of Thermodynamics?

The Second Law of Thermodynamics states that the total entropy of a closed system always increases over time. At constant pressure and volume, the change in entropy is directly related to the heat transferred into the system.

How does temperature affect the entropy of gas at constant pressure and volume?

The temperature of a gas at constant pressure and volume is directly proportional to its entropy. As the temperature increases, the molecules in the gas have more energy and therefore more disorder, resulting in an increase in entropy.

Can the entropy of gas at constant pressure and volume ever decrease?

In accordance with the Second Law of Thermodynamics, the entropy of a closed system can only increase or remain constant. Therefore, the entropy of gas at constant pressure and volume can never decrease.

What is the equation for calculating the change in entropy of gas at constant pressure and volume?

The change in entropy of a gas at constant pressure and volume can be calculated using the equation ΔS = q/T, where ΔS is the change in entropy, q is the heat transferred, and T is the temperature in Kelvin.

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