Thermodynamics Question


by satanic
Tags: expansion, pv=nrt, t1v1=t2v2, thermodyanmics
satanic
satanic is offline
#1
May4-11, 10:31 AM
P: 2
1. The problem statement, all variables and given/known data

A balloon has 0.310 mol of polyatomics gas, Initial volume 7500cm³ and temp 29 degrees C, gas first expands isobarically until volume double. Then expands adiabatiacally until temp returns to initial value, assume gas is ideal gas, C_p = 33.26 J/mol*K, gamma = 4/3.

What is the final volume V?


2. Relevant equations

I think I have to use
PV = nRT
T_1V_1^(gamma-1) = T_2V_2^(gamma-1)

3. The attempt at a solution

I've tried to find the temperature after it expands isobarically and use that as the T1 value, I think this is the only trouble I'm facing here, after that I can find V_2 and add all volumes together, please guide me on how to find T after the isobaric expansion.
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Andrew Mason
Andrew Mason is offline
#2
May5-11, 10:53 AM
Sci Advisor
HW Helper
P: 6,588
Quote Quote by satanic View Post
1. The problem statement, all variables and given/known data

A balloon has 0.310 mol of polyatomics gas, Initial volume 7500cm³ and temp 29 degrees C, gas first expands isobarically until volume double. Then expands adiabatiacally until temp returns to initial value, assume gas is ideal gas, C_p = 33.26 J/mol*K, gamma = 4/3.

What is the final volume V?


2. Relevant equations

I think I have to use
PV = nRT
T_1V_1^(gamma-1) = T_2V_2^(gamma-1)

3. The attempt at a solution

I've tried to find the temperature after it expands isobarically and use that as the T1 value, I think this is the only trouble I'm facing here, after that I can find V_2 and add all volumes together, please guide me on how to find T after the isobaric expansion.
I will assume this is an ideal gas. So PV=nRT which means that T = PV/nR. If P is constant ΔT = ΔV(P/nR). Remember T is in Kelvins so the initial temperature 29C is what in Kelvin?

AM
satanic
satanic is offline
#3
May5-11, 11:32 AM
P: 2
I've actually solved it, thank you anyway


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