Thermodynamics B/C

[Justin72835]

You have a metal pot with heat capacity 540 J/K at a temperature of 114 °C. You then add 350 mL of water at 23 °C into the pot.

a. Is there any steam produced? (yes or no)

b. If yes, then what is the final temperature of the steam? If no, then what is the equilibrium temperature between the water and the pot?

Click to Show Answer

Assuming the whole pot of water has to get to 100 degrees before any steam is produced:

Energy to heat water + energy to boil water + energy to heat steam = energy lost from metal pot.



=> T = -615 degrees Celsius, which is clearly impossible.





=> T = 47 degrees Celsius



a) No

b) 47 degrees Celsius

Nice job; your turn!

[UTF-8 U+6211 U+662F]

Explain why we can make assumptions in the derivation of the ideal gas law, PV = nRT, such as "The number of molecules moving in each axis (x, y, and z) is equal".

[Justin72835]

Explain why we can make assumptions in the derivation of the ideal gas law, PV = nRT, such as "The number of molecules moving in each axis (x, y, and z) is equal".

Answer (Click to Show Hidden Text)

Not really sure about this one. My answer would be that because the molecules are so small, there are so many of them, and they have relatively little interaction with one another, you can assume that all the molecules follow Newton's Law of Motion and collide elastically with each other. From this, you are able to draw other conclusions as well.

[UTF-8 U+6211 U+662F]

Explain why we can make assumptions in the derivation of the ideal gas law, PV = nRT, such as "The number of molecules moving in each axis (x, y, and z) is equal".

Answer (Click to Show Hidden Text)

Not really sure about this one. My answer would be that because the molecules are so small, there are so many of them, and they have relatively little interaction with one another, you can assume that all the molecules follow Newton's Law of Motion and collide elastically with each other. From this, you are able to draw other conclusions as well.

Yep, your turn (Click to Show Hidden Text)

for the record, I was just looking for there being so many molecules that statistical treatment can be applied to them (especially that they have approximately random motion)

[Justin72835]

Two gases occupy two containers, A and B. The gas in A, of volume 0.14 cubic meters, exerts a pressure of 1.18 MPa. The gas in B, of volume 0.21 cubic meters, exerts a pressure of 0.82 MPa. The containers are united by a tube of negligible volume and the gases are allowed to intermingle. What is the final pressure in the container if the temperature remains constant?

[MattChina]

Two gases occupy two containers, A and B. The gas in A, of volume 0.14 cubic meters, exerts a pressure of 1.18 MPa. The gas in B, of volume 0.21 cubic meters, exerts a pressure of 0.82 MPa. The containers are united by a tube of negligible volume and the gases are allowed to intermingle. What is the final pressure in the container if the temperature remains constant?

answer (Click to Show Hidden Text)

0.964?

[Justin72835]

Two gases occupy two containers, A and B. The gas in A, of volume 0.14 cubic meters, exerts a pressure of 1.18 MPa. The gas in B, of volume 0.21 cubic meters, exerts a pressure of 0.82 MPa. The containers are united by a tube of negligible volume and the gases are allowed to intermingle. What is the final pressure in the container if the temperature remains constant?

answer (Click to Show Hidden Text)

0.964?

Not quite. How did you get your answer?

EDIT: This answer is actually correct.

[UTF-8 U+6211 U+662F]

Two gases occupy two containers, A and B. The gas in A, of volume 0.14 cubic meters, exerts a pressure of 1.18 MPa. The gas in B, of volume 0.21 cubic meters, exerts a pressure of 0.82 MPa. The containers are united by a tube of negligible volume and the gases are allowed to intermingle. What is the final pressure in the container if the temperature remains constant?

answer (Click to Show Hidden Text)

0.964?

Not quite. How did you get your answer?

I got the same answer :/ (Click to Show Hidden Text)

Using the law of partial pressures 1.18 MPa * (0.14/0.35) + 0.82 MPa * (0.21/0.35) = 0.964 MPa

[MattChina]

Two gases occupy two containers, A and B. The gas in A, of volume 0.14 cubic meters, exerts a pressure of 1.18 MPa. The gas in B, of volume 0.21 cubic meters, exerts a pressure of 0.82 MPa. The containers are united by a tube of negligible volume and the gases are allowed to intermingle. What is the final pressure in the container if the temperature remains constant?

answer (Click to Show Hidden Text)

0.964?

Not quite. How did you get your answer?

(P1V1/Vf)+(P2V2/Vf)

[Justin72835]

Nevermind, both of you (UTF-8 U+6211 U+662F and MattChina) are right. I messed up my calculations beforehand

Anyways, great job to both of you and sorry for the confusion! I think it's MattChina's turn now.