Cyclic thermodynamics processes

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Homework Help Overview

The discussion revolves around a cyclic thermodynamic process involving a gas, specifically examining the relationship between the change in enthalpy (ΔH) and heat transfer (q). Participants are exploring whether it is valid to assert that ΔH equals q in this context.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants question the definitions of state functions and path functions, with some expressing uncertainty about how to approach the problem. There are inquiries about the implications of a system returning to its original state and what that means for ΔH and q.

Discussion Status

The discussion is active, with participants exploring the implications of ΔH being zero in a cyclic process and questioning the validity of the equation ΔH=q. Some guidance has been offered regarding the definitions of the terms involved, but no consensus has been reached.

Contextual Notes

Participants are grappling with the definitions and relationships between state functions and path functions, as well as the implications of returning to the original state in a cyclic process.

Bipolarity
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Homework Statement


Consider a cyclic process involving a gas. If the pressure of the gas varies during the process but returns to the original value at the end, is it correct to write [itex]ΔH=q[/itex]

Homework Equations





The Attempt at a Solution


I'm actually not sure. q is a path function and H is a state function. To be honest I have no idea how to approach this problem, perhaps someone can give me a small hint.

BiP
 
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How is a state of a gas defined? What is a state function?
Suppose you have a function F(x,y,z) and F(1,2,3)=10 and then you let the variables change, but they return to the original values (1,2,3), what will be F(1,2,3)?

ehild
 
ehild said:
How is a state of a gas defined? What is a state function?
Suppose you have a function F(x,y,z) and F(1,2,3)=10 and then you let the variables change, but they return to the original values (1,2,3), what will be F(1,2,3)?

ehild

So the state of the system has not changed, so the [itex]ΔH[/itex] must be 0. But what about the heat? Must it also be 0?

BiP
 
Bipolarity said:
So the state of the system has not changed, so the [itex]ΔH[/itex] must be 0. But what about the heat? Must it also be 0?

BiP

If ΔH=q and ΔH=0 then what else can q be?

ehild
 
ehild said:
If ΔH=q and ΔH=0 then what else can q be?

ehild

I'm sorry but I am not sure you read the OP. The question asked whether or not [itex]ΔH=q[/itex] ? How can you assume it to be true if you haven't shown it to be true?

BiP
 
You know that ΔH=0 in a cyclic process. Now you need to look after what q and ΔH are, and find out if the equation ΔH=q holds.

ehild
 
Last edited:

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