Find the equation of state of each gas

AI Thread Summary
The discussion revolves around finding the equations of state for different gases using thermodynamic principles. The first gas follows the ideal gas law, while the second gas incorporates corrections for intermolecular forces and volume. Participants highlight the challenge of assuming the right-hand side of the equation as simply nRT and emphasize the need for valid relationships across various temperatures. The concept of treating the equations as functions of temperature is discussed, with clarification that these functions can differ for each gas. The conversation concludes with a suggestion to consider molar volume instead of total volume to simplify the equations.
curious_mind
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Homework Statement
Consider three gases with ##(P_1,V_1),(P_2,V_2)## and ##(P_3,V_3)##. It is found that when the first two are in equilibrium the following condition is satisfied: ##P_1V_1 =\left(P_2 +\frac{a}{V_2^2}\right)(V_2 −b)##, while the equation satisfied when the first and the last are in equilibrium is ##P_3(V_3 −c)=P_1V_1 e^{\frac{−d}{V_3P_1V_1}}##. Find the respective equations of state and identify them.
Relevant Equations
Equation of states of gas at temperature T##f(P,V,T)=0##
The problem is from the book "The Principles of Thermodynamics" by ND Hari dass.

It looks trivial problem, but I am not able to form logical arguements for going into next step.

For example, It seems like first gas has equation of state ##PV =nRT## and second has ## \left( P_2 +\frac{a}{V_2^2} \right) (V_2 −b) = nRT ##
But I cannot straightforward assume Right hand side of equation of state to be simply ##nRT## in general right ? So what could be valid way to proceed from thermodynamical laws ?

Thanks.
 
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For the relationships to hold across all T, each relationship must be of the form (first expression =second expression = some function of T).
 
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If we equate all three relations, then it will be valid only if all three gases in equilibrium, which is not required to be found. We require to find all three gases equation of state separately, at different temperatures.

Also, how can we say that it individual ##f(P,V)## is some function of ##T## ONLY?. Right hand side of equation of state might containt terms like ##\cos (TVe^P)## etc etc or something, in general - right m? Or am I missing something very fundamental?
 
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curious_mind said:
If we equate all three relations
I did not say that. The "some function of T" does not have to be the same for each.
curious_mind said:
Also, how can we say that it individual ##f(P,V)## is some function of ##T## ONLY?.
It is the same principle as "separation of variables" in PDEs.
We know that ##T_1=g_1(P_1,V_1)## and ##T_2=g_2(P_2,V_12)## for some functions ##g_1, g_2##. So at any given temperature T we know ##g_1(P_1,V_1)=g_2(P_2,V_12)##. And these are the forms you are given.
 
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It seems to me your original approach was correct, except I would assume the V is molar volume rather than volume itself, so you would get rid of the n's in the equations.
 
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