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Topic: Work done by a system  (Read 5175 times)

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Offline huskywolf

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Work done by a system
« on: January 02, 2011, 07:40:27 PM »
Calculate  work done by a system in which  formation of 1 mol CO2 gas at 298k and 100kpa, assuming CO2 acts as an ideal gas.

Could you please tell me if I have done this question correctly? ???

w=p(dv)
 
P(dv)=(dn)RT         C(s) + O2(g) :rarrow: CO2(g)

dn=1-2=-1

(dv)=[(-1)(8.314)(298)]
(dv)=-24.77

w=(100)(-24.77)= -2477 J (Exothermic)

Offline huskywolf

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Re: Work done by a system
« Reply #1 on: January 03, 2011, 05:31:11 AM »
Is this is trick question please?
The work done is just the enthalpy of formation?

Please answer .
Thank you sir

Offline TIGERHULL

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Re: Work done by a system
« Reply #2 on: January 06, 2011, 06:24:06 PM »
It's kPa, not just Pa. Also, what are you forming CO2 from, carbon and oxygen?

Offline unknown_analysis

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Re: Work done by a system
« Reply #3 on: January 08, 2011, 10:12:45 AM »
work = -P( :delta: V)

so,

work = - :delta: nRT

work = - (-1 mol)(8.314 J/mol K)(298 K)

work = 2477.572 J



Reference:
Petrucci, et. al. General Chemistry Principles and Modern Applications. 8th Edition. Prentice-Hall 2002

Cheers,
unknown_analysis

Offline huskywolf

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Re: Work done by a system
« Reply #4 on: January 10, 2011, 05:01:23 PM »
Actually I got 2.357 atmL or ,239 Joules for the answer to this question.

PV=nRT
V= (1)(0.0821Latm/molK)(298k)/(0.987)
V=24.78L
dV= 24.78L - 22.4L = 2.38L
w=-p(dV)
w=-(0.987atm)(2.38L) =2.357 atmL or ,239 Joules?

Offline rabolisk

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Re: Work done by a system
« Reply #5 on: January 11, 2011, 01:36:06 PM »
I believe that the answer should be 0.

Offline huskywolf

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Re: Work done by a system
« Reply #6 on: January 11, 2011, 02:07:38 PM »
I believe that the answer should be 0.

Would you like to elaborate on that?

Offline rabolisk

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Re: Work done by a system
« Reply #7 on: January 11, 2011, 08:32:35 PM »
If you assume that the volume of the solid carbon is negligible compared to the volume of the gases, then you are going from 1 mole of gas to 1 mole of gas, both assumed to behave ideally. There is no volume change, and thus, no work.

Offline huskywolf

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Re: Work done by a system
« Reply #8 on: January 12, 2011, 07:53:11 AM »
If you assume that the volume of the solid carbon is negligible compared to the volume of the gases, then you are going from 1 mole of gas to 1 mole of gas, both assumed to behave ideally. There is no volume change, and thus, no work.
That makes sense,thanks.

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