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Topic: relationship between equilibrium and deltaG  (Read 3723 times)

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Offline pepocho

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relationship between equilibrium and deltaG
« on: April 16, 2013, 11:22:56 PM »
i was trying to find the Kp of a problem. Long story short, the correct formula was deltaG=-RTlnK. After finding K, i used the equation Kp=KRT^(deltaN) but that turned out to be wrong. So i was wondering why is that wrong? I added a photo of the problem

Offline Corribus

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Re: relationship between equilibrium and deltaG
« Reply #1 on: April 17, 2013, 12:20:14 AM »
It's hard to see what the question is from the image.  There is a scroll bar and it's unclear what part of the question you are having difficulty with.

If you want help, please take the time to retype the question here and format your equations properly.  "Long story short" isn't helpful.  Explain exactly what you did.  Then it is easier to analyze what you're doing wrong and help you.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline pepocho

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Re: relationship between equilibrium and deltaG
« Reply #2 on: April 17, 2013, 12:30:45 AM »
i put in a horrid image, i am sorry. i tried to reupload it with a better quality. Hopefully this one works. My problem is with the equation deltaG= -RTlnK. It is asking for the Kp of the equation, so after using that equation to find K, i would assume i would need to use another equation Kp=K(RT)^deltaN. however after using this equation, the answer was marked wrong. the right answer was just the K constant from the equation deltaG=-(RT)(lnk). So my question is why is K=Kp in this problem?

P.S. if picture is still cruddy i will retype the question

Offline Arkcon

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Re: relationship between equilibrium and deltaG
« Reply #3 on: April 17, 2013, 06:40:10 AM »
P.S. if picture is still cruddy i will retype the question

We'd prefer you did that from the beginning, yeah.  Writing the problem out, removing extra information, rewriting what's needed is a good way to help yourself figure out what the question is actually about.  You might even solve the problem yourself in the process.  If nothing else, you can at least crop the screen image -- no one needs the white space, the Windows tab bar listing all other open apps, and the screen's bottom bar to help you solve it.  Like this:
« Last Edit: April 17, 2013, 12:14:18 PM by Arkcon »
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Corribus

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Re: relationship between equilibrium and deltaG
« Reply #4 on: April 17, 2013, 09:40:46 AM »
Yes, much better!  But the "main question" box still has a scroll bar so we only see a portion of it.  It's still hard to know everything that's being asked. 

And in any case, the OP needs to explain exactly what he did.  A lot was glossed over by "a long story short". :)
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Big-Daddy

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Re: relationship between equilibrium and deltaG
« Reply #5 on: April 17, 2013, 01:42:16 PM »
Well from the outside perspective most of the problem is unsolvable given you've hidden the data ...

OP your problem may have been an incorrect use of the equation you listed. Firstly, delta n is the number of moles of gas in the products minus the number of moles of gas in the reactants for one mole of the equation; secondly, the equation actually must be seen as Kp=Kc*(RT)^(delta n_gas). Keep the RT and brackets and try again is my guess.

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