Compression of monatomic ideal gas

[zygisyyy]

a monatomic ideal gas initially at 17°C is suddenly compressed to one-tenth its original volume. What is the tmeperature after copression? make the same calculations for a diatomic gas.

 

[kuruman]

Hi zygisyyy and welcome to PF. Please follow the rules of this forum and use the template when you seek help with homework. Show us the relevant equations and tell us what you tried and what you think about the problem. We just don't give answers away.

 

[zygisyyy]

Hi, I thought maybe equation pV=nRT may work, but when i tried entering the values into the equation the answer was wrong ( near the proplem there are answers 1350 K for monatomic gas and 730 K for diatomic ). Then I tried surfing the web and found that the dimensionless specific heat capacity is 3/2 for monatomic gases and 5/2 for diatomic gases, but it said that it is so when the volume is constant. And I don't know what to do else.

 

[kuruman]

This problem needs to be done using the First Law of Thermodynamics, not the ideal gas law. Hint: "Sudden compression" means that the gas is squeezed so fast that heat does not have a chance to enter or leave the gas. What does the First Law become in this case?

 

[zygisyyy]

so i should use U=3/2*m/M*R*T?
or calculate as the sum of potential and kinetic energies? But i don't know the formula for the potential energy of monatomic and diatomic gases

 

[kuruman]

What is an equation that expresses the First Law of Thermodynamics?

 

[zygisyyy]

Q + A = delta U

 

[kuruman]

OK, now the process in which no heat goes in and out of the system is an adiabatic process. for which pV^γ = constant. Have you seen this equation?

 

[zygisyyy]

thanks. now i know how to solve this equation