Fundamentals of Chemical Engineering: [One Question per Day] 2011-02-01
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This post was last edited by sailan on 2011-2-9 10:37. Choose the correct answer for the reasoning question: For an isothermal expansion of an ideal gas, let the changes in internal energy and enthalpy before and after the process be denoted as X and Y respectively. Then, what is the relationship between X and Y? ( ) A. X > Y B. X
Reply 1# yunzhongzi112: A dH = dU – TdS, and since dS > 0, it follows that dU > dH
H=U+PV, dU=TdS-PdV, dH=TdS+VdP. For an ideal gas undergoing isothermal expansion, the values of these changes are all equal to ∫PdV=∫VdP=RTln(V1/V2)=RTln(P2/P1). So the changes should be equal. Uh, I forgot which option it was……
This post was last edited by sailan on 2011-2-1 08:06; the answer is c
This post was last edited by sailan on 2011-2-1 08:08: d...................
Reply 1# yunzhongzi112 c