PS4KEYF07 - Chemistry 391 PS4 KEY 1. Fall 2007 a) The gas...

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1 Chemistry 391 Fall 2007 PS4 KEY 1. a) The gas is heated from 300 K to 450 K at a constant external pressure of 1.00 bar. -1 -1 -2 3 5 1 mol 8.314 J mol K 300 K 2.49 10 m 10 Pa i i i nRT V P ×× == = × -2 3 -2 3 450 K 2.49 10 m = 3.74 10 m 300 K f fi i T VV T × × × () 5- 2 3 - 2 3 3 10 Pa 3.74 10 m 2.49 10 m 1.25 10 J external wP V =− Δ =− × × × × -1 -1 3 , 3 8.314 J mol K 1 mol 150 K = 1.87 10 J 2 Vm Un C T × Δ= × × × 333 1.87 10 J + 1.25 10 J = 3.12 10 J qHU w =Δ =Δ − = × × × -1 -1 -1 , 34 5 0 K ln 1 mol + 1 8.314 J mol K ln = 8.43 J K 2 300 K f Pm i T Sn C T ⎛⎞ = × × × ⎜⎟ ⎝⎠ b) The gas is heated to 450 K at a constant volume corresponding to the initial volume. w = 0 because Δ V = 0. -1 -1 3 , 3 8.314 J mol K 1 mol 150 K = 1.87 10 J 2 Uqn × Δ== × × × -1 -1 3 , 5 8.314 J mol K 1 mol 150 K = 3.12 10 J 2 Hn × × × × -1 -1 -1 , 3 450 K ln 1 mol 8.314 J mol K ln = 5.06 J K 2 300 K f i T C T = × × × c) The gas undergoes a reversible isothermal expansion at 300 K until the pressure is half of its initial value. Δ U = Δ H = 0 because Δ T = 0.
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This note was uploaded on 07/25/2008 for the course CEM 391 taught by Professor Cuckier during the Fall '08 term at Michigan State University.

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PS4KEYF07 - Chemistry 391 PS4 KEY 1. Fall 2007 a) The gas...

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