Seeming simple Thermodynamics problem

In summary, a balloon is initially inflated with 5 liters of monatomic gas at 0 degrees Celsius and is then heated to 60 degrees Celsius at 1 atm pressure. Using the ideal gas law, the amount of gas in the balloon can be calculated to be 0.222601 moles. The heat absorbed by the gas at constant volume is approximately 166J. If the balloon expands freely at constant pressure, the work done by the gas is 111J, taking into account the mass flowing into the system and potential boundary work.
  • #1
StickNinja
3
0
A balloon is inflated with 5 liters of monatomic gas at 0 degrees Celsius and heated to 60 degrees Celsius at 1 atm. pressure.
R=8.31J/mol K, Cp=5R/2, and Cv = 3R/2

1. If the balloon does not expand, the heat absorbed by the gas would be what?
2. If the balloon expands freely at constant pressure, the work done by the gas would be what?

...Took me a while, but I figured it out (no mass is entering the system). So here is the solution in case others want to know.

For #1 PV=nRT
P=1 atm=1.01*10^5 Pascals
V=5 liters=.005 m^3
n=Unknown
R=8.31 J/mol K
T=273K, Given

Solving for n, we get .222601 mols

ΔU=nCvΔT --constant volume
ΔU=n*3R/2*60= 166J roughlyFor #2

ΔU=nCpΔT
ΔU=277.47
ΔU=Q+W
W=111J
 
Last edited:
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  • #2
You'll have to take into account the mass flowing into the system. There may also be boundary work involved.
 

1. What is thermodynamics?

Thermodynamics is the branch of science that deals with the study of heat and its transformation into other forms of energy.

2. What is a simple thermodynamics problem?

A simple thermodynamics problem is one that involves the calculation of heat transfer, work, or changes in temperature of a system using basic thermodynamic equations.

3. How do I approach a simple thermodynamics problem?

First, identify the variables given in the problem and the ones you need to find. Then, choose the appropriate thermodynamic equations to solve for the unknown variable. Finally, plug in the values and solve for the unknown variable.

4. What are some common mistakes when solving simple thermodynamics problems?

Some common mistakes include not converting units properly, using incorrect thermodynamic equations, and not considering the signs of the variables (positive or negative) in the equations.

5. Can I use ideal gas law in simple thermodynamics problems?

Yes, the ideal gas law (PV = nRT) can be used in simple thermodynamics problems involving ideal gases. However, it should be noted that this law is only applicable to ideal gases under certain conditions.

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