Change in entropy for adiabatic compression

Click For Summary
The discussion focuses on calculating the change in entropy for adiabatic compression of nitrogen gas. The user has determined values for Cv and Cp and the change in volume but is uncertain about finding the change in pressure and temperature. They note that since nitrogen behaves as an ideal gas, the ideal gas law (PV=nRT) can be applied, but it requires knowing the temperature change. The adiabatic condition, which relates pressure and volume through the specific heat ratio (γ), is suggested as a necessary approach to find the change in pressure. The conversation emphasizes the importance of understanding the relationship between pressure, volume, and temperature in adiabatic processes.
Bugsy23
Messages
24
Reaction score
0

Homework Statement



A sample of 8.02*10^-1 moles of nitrogen gas (\gamma=1.4) occupies a volume of 2*10^-2m^3 at pressure 1*10^5pa and temperature 300K. The gas is adiabatically compressed to half its original volume. What is the change in entropy of the gas?


Homework Equations



S2-S1=CvIn(P2/P1)+CpIn(V2/V1)

PV=nRT

The Attempt at a Solution



I have already worked out the values for Cv and Cp and the change in volume of the gas, but I don't know how to find the change in pressure. Since nitrogen behaves as an ideal gas, it should be possible to find it using PV=nRT, but that also requires knowing the change in temperature. Is there a different way of working out the change in pressure?
 
Physics news on Phys.org
You have to use the adiabatic condition. This condition shows the relationship between P and V in an adiabatic change. Hint: it uses \gamma

AM
 

Thread 'Magnitude of buoyant force in fluids of different densities'

The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?
View full post »

Similar threads

Entropy Change Confusion
  • · Replies 7 ·
Replies
7
Views
1K
Adiabatic condition and equation of state
  • · Replies 7 ·
Replies
7
Views
3K
Adiabatic Expansion of Pressurized Air in a Piston-Cylinder Setup
  • · Replies 8 ·
Replies
8
Views
2K
Isothermic and adiabatic compression
  • · Replies 17 ·
Replies
17
Views
2K
Finding the pressure of a gas in three identical balloons
  • · Replies 12 ·
Replies
12
Views
2K
Gas temperature in a constant volume
  • · Replies 8 ·
Replies
8
Views
2K
Work done in adiabatic process vs work done in isothermal
  • · Replies 2 ·
Replies
2
Views
3K
Thermally insulated container with alternating series of walls
  • · Replies 49 ·
2
Replies
49
Views
3K
What is the volume of the gas after adiabatic compression
  • · Replies 2 ·
Replies
2
Views
1K
Change in entropy of an ideal gas during thermodynamic cycle
  • · Replies 1 ·
Replies
1
Views
2K