Go Back   Physics Help Forum > High School and Pre-University Physics Help > Thermodynamics and Fluid Mechanics

Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

Reply
 
LinkBack Thread Tools Display Modes
Old Aug 17th 2016, 02:56 PM   #1
Junior Member
 
Join Date: Aug 2016
Posts: 4
Changing state of an ideal gas

Hello everyone, I've been given following question:

"An ideal gas is enclosed in a container at state (p1,V1,T1). It is desired to change the state of the gas to (2p1,V1,2T1).
This has to be done by only two processes (i.e isothermal followed by isobaric) the processes can't be of the same type.
The processes are to be chosen between adiabatic, isobaric, isochoric, and isothermal.
In how many ways can this be done?"

My thinking is that i can do at least the following:

Isochoric -> to some temperature and pressure -> adiabatic to the desired state

The reverse

Isochoric -> to some temperature and pressure -> isothermal to the desired state

The reverse

Adiabatic -> to the correct temperature curve -> isothermal to the desired state

The reverse

Leaving me with 6 different ways to solve the problem. Is this right way of thinking? And is my attempt even correct?

Thank you very much in advance.
Linder is offline   Reply With Quote
Old Aug 17th 2016, 03:03 PM   #2
Senior Member
 
Join Date: Apr 2015
Location: Somerset, England
Posts: 1,035
What makes you think this is possible?
studiot is offline   Reply With Quote
Old Aug 17th 2016, 03:11 PM   #3
Junior Member
 
Join Date: Aug 2016
Posts: 4
Well as p1,V1 and T1 can be chosen arbitrarily together with the ideal gas, I see no reason why this should not be possible?
Linder is offline   Reply With Quote
Old Aug 18th 2016, 12:30 AM   #4
Senior Member
 
Join Date: Apr 2015
Location: Somerset, England
Posts: 1,035
Well as p1,V1 and T1 can be chosen arbitrarily together with the ideal gas
Can they?

Under what circumstances?

Look carefully at the equation of state for an ideal gas.

If the above is to be true what needs to change to also make

2p1, V1 and 2T1 possible?
studiot is offline   Reply With Quote
Old Aug 18th 2016, 02:05 AM   #5
Junior Member
 
Join Date: Aug 2016
Posts: 4
Can they?
Hmm well if the gas is ideal then the following relation should be true:

PV=nRT

with R as the gas constant. "n" the number og moles, and P,V,T as pressure, volume and temperature.

But as for the state (p1,V1,T1), the volume will most likely be preset by the size of the container,
so once that is chosen then choosing either p1 or T1 will restrain the other one.
I mean if one were to chose p1 then the temperature will be given as T = PV/nR,
and choosing T1 the pressure will be given as p =nRT/V.

And for the rest of I can only guess unfortunately.
Linder is offline   Reply With Quote
Old Aug 18th 2016, 03:45 AM   #6
Senior Member
 
Join Date: Apr 2015
Location: Somerset, England
Posts: 1,035
So you cannot choose P, V and T independently for a given quantity of gas.

The only way choose all three is to play with n, the quantity of gas.
studiot is offline   Reply With Quote
Old Aug 18th 2016, 03:56 AM   #7
Junior Member
 
Join Date: Aug 2016
Posts: 4
Okay I see, but let's say we fix the quantity of the gas in a closed container, and we then measure the initial state to be (p1,V1,T1). Is it then possible to change the state to (2p1,V1,2T1) at all or is my guess of 6 path way off?
Linder is offline   Reply With Quote
Old Aug 18th 2016, 04:33 AM   #8
Senior Member
 
Join Date: Apr 2015
Location: Somerset, England
Posts: 1,035
If the above is to be true what needs to change to also make

2p1, V1 and 2T1 possible?
That is why I asked you to think about this.

If you are going to maintain the volume, whilst also specifying the pressure and temperature, you will have to change the quantity of gas.
studiot is offline   Reply With Quote
Reply

  Physics Help Forum > High School and Pre-University Physics Help > Thermodynamics and Fluid Mechanics

Tags
changing, gas, ideal, state



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Changing a diagonal operator from position to momentum roger Quantum Physics 0 Mar 31st 2015 01:17 PM
Why lines changing wide and Hz ( 24h test ) mmmmm Advanced Optics 0 Feb 28th 2014 10:42 AM
Question on electron going from state 4 to ground state s3a Atomic and Solid State Physics 3 Oct 8th 2011 11:44 PM
Changing the course of an asteroid? fallschirm2 Kinematics and Dynamics 2 May 22nd 2009 11:33 AM
Pendulum with changing length zenctheo Advanced Mechanics 3 May 13th 2008 05:02 AM


Facebook Twitter Google+ RSS Feed