Thermodynamics Help: Ideal Gas Temperature Rise Comparison

[zorro]

Homework Statement

Two cylinders A and B fitted with pistons contain equal number of moles of an ideal monoatomic gas at 400K. The piston of A is free to move while that of B is held fixed. Same amount of heat energy is given to the gas in each cylinder. If the rise in temperature of the gas in A is 42K, the rise in temperature of the gas in B is

a)21K
b)35K
c)42K
d)70K

The Attempt at a Solution

Going by the options, the answer should be d) because the entire heat supplied is used to raise the internal energy of the gas in container B where as some part of it is used to do work against the piston in container A (work on expansion). But this is incorrect.

 

[Andrew Mason]

Homework Statement

Two cylinders A and B fitted with pistons contain equal number of moles of an ideal monoatomic gas at 400K. The piston of A is free to move while that of B is held fixed. Same amount of heat energy is given to the gas in each cylinder. If the rise in temperature of the gas in A is 42K, the rise in temperature of the gas in B is

a)21K
b)35K
c)42K
d)70K

The Attempt at a Solution

Going by the options, the answer should be d) because the entire heat supplied is used to raise the internal energy of the gas in container B where as some part of it is used to do work against the piston in container A (work on expansion). But this is incorrect.

d) is the correct answer. The ratio of the temperature of B to that of A is Cp/Cv = 5/3. 5x42/3 = 70

AM

 

[zorro]

Thanks!

 

[Andrew Mason]

d) is the correct answer. The ratio of the temperature of B to that of A is Cp/Cv = 5/3. 5x42/3 = 70

I meant to say of course that the ratio of the "change in" temperature of B to that of A is Cp/Cv.

AM