# Cyclic thermodynamics processes

## 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 $ΔH=q$

## 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

## The Attempt at a Solution

ehild
Homework Helper
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

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 $ΔH$ must be 0. But what about the heat? Must it also be 0?

BiP

ehild
Homework Helper
So the state of the system has not changed, so the $ΔH$ 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

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 $ΔH=q$ ? How can you assume it to be true if you haven't shown it to be true?

BiP

ehild
Homework Helper
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

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