Free expansion Definition and 34 Threads

I proceeded in the usual manner in which we take ##dU = 0## in the case of free expansion because there is no heat transfer in the box, as well as no work is done. We can write, taking ## U ## as the function of ##V## and ##T##, $$ dU(V,T) = \left( \dfrac{\partial U}{\partial V} \right)_T ~...

For a freely expanding ideal gas(irreversible transformation), the change in entropy is the same as in a reversible transformation with the same initial and final states. I don't quite understand why this is true, since Clausius' theorm only has this corrolary when the two transformations are...

Hey all. I'm trying to understand the evolution of the velocity distribution function of a gas undergoing free expansion. I know that at t=0, the velocity distribution function is given by ##u(t=0, x)=Ax^{1/2}##, where ##A## is a known constant. From the momentum equation, I have: ##du/dt+u...

Hi everyone, I am confused when I apply Euler's equation on the free expansion of an ideal gas. Consider a free expansion (expansion of gas in vaccum) where the volume is doubled (V->2V) The classical free expansion of an ideal gas results in increase in entropy by an amount of nR ln(2), a...

Previous of this problem, there was another problem. that is "What is the change in Temperature of van der Waals gas in free expansion?". I got them. It was C_V dT= -aN^2/V^2 dV Then, I got T=T0-aN^2/2VC_V So i knew that the Temperature is decreased by free expansion in adiabatic process. Then I...

Homework Statement After a free expansion to quadruple its volume, a mole of ideal diatomic gas is compressed back to its original volume isobarically and then cooled down to its original temperature. What is the minimum heat removed from the gas in the final step to restoring its state...

If considering the free expansion of an ideal gas adibatically such that the final volume is double of the initial volume. Since dU=0 for free expansion ,which implies Ti=Tf for ideal gas...(1) From adiabatic relation , TiViγ-1=TfVfγ-1, to satisfy (1) ,γ-1=0 and for ideal gas Cp-Cv=nR or...

Good day all! I have the following exercise One kilo-mole of air expands adiabatically from an initial state p1=1 bar, T1=340 K to a final state V2= 2V1. Compute the temperature of the final state, for the following cases: Joule expansion (gas free expansion with W12=0) My problem is with the...

I am writing a document on the Joule-Thomson effect. But in my research for it I have come across something that I am not completely clear on. In my document I explained the free expansion of an ideal gas and am trying to transition/segue into the Joule-Thomson effect. However now I am having...

If a gas is suddenly allowed to expand freely and adibatically inside a container then from the first law of thermodynamics dQ=0, My question is whether the change of internal energy would be 0 and if it then how would the work done be 0 (since accessible volume of the gas changes inside the...

Homework Statement The question is: What happened with the entropy in a free expansion? The system is isolated and the state equation is: $$p=AT/V+B/V^2$$ Homework Equations $$dU=TdS-pdV$$ The Attempt at a Solution My attempt is: Because the system is isolated and corresponding to an free...

I learned that $$ dS = \frac Q T$$ In free expansion of Ideal gas, it is obvious that Q = 0. However, the entropy increases. I guess the reason is that it is because the process is not quasistatic. If I am right, why is this process not quasistatic. If I am not, what's wrong with the formula...

We have 2 (insulated) partitions, one with the gas, another vacuum, separated by a stop cock. We remove the cock, letting the gas expand into vacuum . I understand that since there is no opposing force on the expanding gas ,the work done by the gas is zero . But work done by gas is given by...

ΔU=q-w and in a free expansion w=0 and Free expansion is an irreversible process in which a gas expands into an insulated evacuated chamber. Does this mean that free expansion is an isolated system? Meaning the walls of the container are adiabatic in which no heat can enter the system and so q=0...

From a video lecture, it is mentioned that "dU≠dW in Joule's free expansion if the process is irreversible and adiabatic" Mentioned in around 36:00-38:00 in the video: What I would like to ask is why in this irreversible adiabatic process, dU≠dW? Is it because the W here doesn't include other...

Homework Statement Consider an ideal monatomic gas that undergoes an adiabatic free expansion starting from equilibrium state A with volume 500 cm3, pressure 40 kPa and temperature 300K to state B, which has a final equilibrium volume of 1000 cm3. Construct an reversible isothermal path that...

Hello PF! Consider the free expansion of an ideal gas. The process occurs at constant temperature, therefore, ΔU = 0, Q = 0, and W = 0. Suppose we are given the initial and final pressures of the gas, and we calculate ΔG = nRT ln(P2/P1). As P2 < P1, ΔG < 0. This is intuitive, as a free expansion...

Hello! Today I've learned that when a Van der Waals gas undergoes a free expansion, it cools down a bit. :bugeye: This is in contrast with the ideal gas in which case since it does no work and since the process is adiabatic, the internal energy of the ideal gas remains unchanged by the...

Let's consider free expansion of an Ideal gas into vacuum. We have 2 (insulated) partitions, one with the gas, another vacuum, separated by a stop cock. I lift the cock, letting the gas expand into vacuum. I am aware that in free expansion of a gas into vacuum, the change in internal energy i.e...

A typical free expansion scenario described in texts is that of a gas confined to a thermally insulated container with a removable membrane. When the membrane is removed the gas expands into vacuum. I understand that no work can be done because the gas does not exert a force. However, I am...

Homework Statement A rigid ( ie. Constant volume), non-conducting ( ie. Perfectly insulated, no heat losses or gain) tank with a volume of 4.6 m^3. The tank is divided into two unequal parts by a thin membrane. One side of the membrane representing 1/3 of the tank is filled with nitrogen ( may...

Hello! I was thinking about what would happen if an atomic gas was allowed to expand in vacuum and concluded I don't have much of a handle on the subject, so if anyone would help me out - I'd really appreciate it. So, let's say we have an ideal gas in a container located in vacuum...

Homework Statement prove that for a free expansion the following equality holds: \left( \frac{\partial T}{\partial V} \right) _{U} = - \frac{1}{C_{V}} \left[ T \left(\frac{\partial P}{\partial T} \right)_{V} - P \right]Homework Equations thermodynamic potentials, maxwell equations etc.The...

I searched in the fora, and I did find https://www.physicsforums.com/showthread.php?t=292278" asking pretty much the same thing. Internal energy change and work done are zero, so no heat is absorbed. Thus entropy is zero, hence it isn't spontaneous. What am I doing wrong? Could you also...

Suppose there are two parts in an insulated chamber, one filled with ideal gas and other is complete vaccum, separated by a partition. Now if partition is removed then gas will rush in other part to fill the whole chamber. PROBLEM- Now there should be increase in entropy of system but i have...

I hope someone in here can help me out of this problem. I know that for calculating the change in entropy of a system (\Delta S) we can use this formula : \Delta S=\int[SIZE="4"]δq/T Well the problem is here, when we calculating ΔS for an adiabatic process we know Q= 0 so ΔS=0 in this...

Homework Statement There are two vessels connected by a stopper. Both have the same volume. One has "N_a" moles of gas, the other "N_b". Find the expression for the change in temperature when the stopper is opened and the system is allowed to come to a new equilibrium state. The...

Hello. This is my first post in this forum, so bear with me on any flaw or mistake please. Homework Statement Imagine a gas confined within an insulated container as shown in the figure below. The gas is initially confined to a volume Vi at pressure Pi and temperature Ti. The gas then is...

I know that the work done on the system in any free expansion is 0 since the external pressure is 0. However.. is q necessarily 0? Does the temperature necessarily stay constant for an ideal gas? I've been trying to justify the reasons for which q is necessarily 0, but I can't find a...

Hello, I have a small problem concerning the free expansion of a gas. https://www.physicsforums.com/attachment.php?attachmentid=20388&stc=1&d=1252066499 The two chambers are separated by a movable piston (without friction). Obviously the gas will expand because it puts pressure p on the...

Homework Statement A gas obeys the Van Der Waal equation of state. The gas undergoes a free expansion from volume Vi to Vf at a constant temperature T. Find the change in entropy of the gas.Homework Equations du=Tds-Pdv+mdn The Attempt at a Solution I can solve the problem assuming du= 0 but...

what happens in a free expansion?

Why does free expansion represent the limit of irreversibility at which all of the "potential" work is degraded to heat.

For the free expansion of an ideal gas into an evacuated chamber, I know that Work=0 and Q=0. Correct? This implies that the change in internal energy dU also equals 0. Since U depends solely on T, this should mean that the final temperature of the chamber is equal to the temperature of the...