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Topic: Adiabatic expansion of ideal gas  (Read 5061 times)

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Offline Naumans

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Adiabatic expansion of ideal gas
« on: October 04, 2008, 09:36:28 PM »
Hey everyone just had a bit of trouble solving this problem, hope someone can help. thanks in advance

A system initially consists of 15.00 moles of N2(g) at a pressure of 3.59 bar inside a 103 liter
adiabatic container with rigid walls, plus a syringe containing 3.00 moles of liquid hydrazine,
N2H4(l), which has a volume of 95.2 cm3. Both the N2(g) and the N2H4(l) are initially at a
temperature of 295 K. The hydrazine is injected into the insulated container and then
decomposes according to:

N2H4(l) ==> N2(g) + 2H2(g)

The final temperature is found to be 535 K and the pressure is 10.42 bar. Deviations of the
gas properties from ideal behavior are significant under these conditions.

Calculate (delta) U and H for this process?

Hears what i thought Since the process is adiabatic, U = w.

w=-p(V2-V1) and U= q(constant volume)=C(constant volume)(T2 - T1)

somehow manipulating this and H= U + PV i hope to get the answer.

???
 
Thanks again.

P.S : By the way this question does have a quantitative answer even though it say this (Deviations of the
gas properties from ideal behavior are significant under these conditions.)??




Offline enahs

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Re: Adiabatic expansion of ideal gas
« Reply #1 on: October 04, 2008, 10:19:26 PM »
For an Ideal Gas, Cv,m = 3/2 R (Cp,m = 5/2 R).

But if it says they might behave significantly different in these conditions, perhaps they want you to use the equation for C as a function of temperature (usually in the back of the book with the appendix that contains various C's).

Offline Naumans

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Re: Adiabatic expansion of ideal gas
« Reply #2 on: October 04, 2008, 10:51:08 PM »
no other values for this question were given other than those stated

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