# I What will be the flow direction?

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1. May 26, 2016

### Ravi Singh choudhary

I guess there would be no flow in case 2; case 3 seems easy to me applying fluid mechanics principle; flow will be 1 to 2. But I doubt case 1; it is not in thermal equilibrium ??? Pls help

2. May 26, 2016

### Staff: Mentor

Can heat flow between the two chambers, or are the insulated from one another?

3. May 26, 2016

### BvU

You may assume the system will tend to go to equilibrium. What does that mean for T1 and T2 ? If they don't stay the same, then what does the change in T1 mean for P1 ?

4. May 26, 2016

### Ravi Singh choudhary

Yeah, heat flow is allowed between chambers;
What you are seeing is just a valve between two chambers.

5. May 26, 2016

### Ravi Singh choudhary

It doesn't seem practical to me also. So pls answer one that you want to acknowledge.

6. May 26, 2016

### BvU

Could you replhrase ? I don't understand what you are trying to tell me. Basically I don't answer: I help answering by asking questions. About case 1.

7. May 26, 2016

### Ravi Singh choudhary

Pressure is equal before; but temperature T1 is more----> They would try to attain the thermal equilibrium. When valve is being opened; I don't know what would happen; simply because I am not able to think; because I don't have numerical values how can I compare the density (say). I could say if there is density variation due to temperature difference simply flow will be from higher density to lower density side.

8. May 26, 2016

### BvU

You have the ideal gas law for guidance.

9. May 27, 2016

### gracy

Is it right approach?

10. May 27, 2016

### BvU

Check out $p_1V_1 = n_1RT_1$ in combination with $p_2V_2 = n_2RT_2$ in combination with $p_1 = p_2$, $V_1=V_2$ and $T_1 > T_2$. What about $n_1'$ and $n_2'$ after equilibrium is established ?

11. May 27, 2016

### gracy

Why can't we apply simple fundamental principle that heat flows from higher temperature to lower temperature?

Last edited: May 27, 2016
12. May 27, 2016

### BvU

We do apply that. But to answer the question what that means for the material flow we need a follow-up step.

13. May 27, 2016

### Staff: Mentor

CASE 1: According to the ideal gas law, how many moles of gas are present in container 1 before the valve is open? How many moles of gas are present in container 2 before the valve is open? Does the total number of moles of gas in the two containers change after the valve is open? In the final equilibrium state, are the temperatures in the two containers (a) the same or (b) different? (If they are the same, then call that T). Does the overall system do any work on the surroundings? Does the overall system exchange any heat with the surroundings? From the first law of thermodynamics, what does that tell you about the change in internal energy of the overall system? From this, what is the final temperature? What is the final pressure? What are the final number of moles of gas present in container 1? How does that compare with the initial number of moles of gas present in container 1?

14. May 27, 2016

### Staff: Mentor

Better yet, if the final temperatures, pressures, and volumes are equal, what does that tell you about the final ratio of the number of moles of gas in each container?

15. May 27, 2016

### Ravi Singh choudhary

That means in all the cases; simply we have to find the ratio of moles of two chamber. Flow direction will be from higher to lower number of moles.

16. May 27, 2016

### Staff: Mentor

Not in case 2. In case 2, there will be no flow even though there are more moles in chamber 2.

17. May 27, 2016

### Ravi Singh choudhary

I think more moles will in chamber 1 in case 2.

18. May 27, 2016

### Staff: Mentor

Sorry. I got it backwards.