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thermodynamics graph problem

 
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kcband



Joined: 20 Feb 2012
Posts: 1
Location: seattle

PostPosted: Mon Feb 20, 2012 9:19 pm    Post subject: thermodynamics graph problem Reply with quote


Look at the graph and answer the questions below. The graph of pressure P versus V shows the expansion of 2.0 moles of a monatomic ideal gas from state A to state B. Pa=Pb=600N/m^2, Va = 3.0m^3 and Vb = 9.0m^3.

1. Calculate the work done BY THE GAS as it expands.

2.Calculate the change in internal energy of the gas as it expands.

3.Calculate the heat added to or removed from the gas during this expansion.

Any help would be great thanks.
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hepcj
Site Admin


Joined: 23 Jun 2007
Posts: 125

PostPosted: Tue Feb 21, 2012 12:13 am    Post subject: Reply with quote

These questions are an application of the first law of thermodynamics.
dU = dQ - dW ---------------(1)

or change in internal energy = heat input - work out

Work done by gas is:
W = P dV
=> W = P [Vf - Vi]

This expansion is at constant pressure therefore dU =0.

Therefore from (1), dQ = dW. or the heat is added to the system is equal to the work done.
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