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Topic: solubility solve for ksp  (Read 18717 times)

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Offline plasticfood

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Re: solubility solve for ksp
« Reply #15 on: November 13, 2011, 09:47:07 PM »
oh crap i forgot to convert my temps to kelvin, hold on..

Offline UG

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Re: solubility solve for ksp
« Reply #16 on: November 13, 2011, 09:53:29 PM »
My line of best fit came out at y = -7896.2x + 4.0345
The two methods produce similar results

Offline plasticfood

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Re: solubility solve for ksp
« Reply #17 on: November 13, 2011, 09:56:33 PM »
ok i regraph mine b/c i forgot to convert my temps to kelvin :p

i got y = -7904.2x + 4.0493

delta H = 65715.52
delta S = 33.67

mmm it's the same thing but the negatives are reverse.

Offline UG

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Re: solubility solve for ksp
« Reply #18 on: November 13, 2011, 10:01:21 PM »
Don't think anything is wrong, the slope of my first graph should be -ΔS so then ΔS works out to be positive. Plus I used 273.15 K and 373.15 K for the temperature and didn't round anything so our numbers are bound to be slightly different

Offline plasticfood

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Re: solubility solve for ksp
« Reply #19 on: November 13, 2011, 10:04:51 PM »
mmm that's strange, but what about the second graph? the y-intercept is positive, so delta S should be positive.   

Offline UG

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Re: solubility solve for ksp
« Reply #20 on: November 13, 2011, 10:08:09 PM »
Yes, ΔS is meant to be positive, you can just work it out by 4.0345*8.314 = 33.54 J K-1 mol-1
Its just that the equation for my first graph is ΔG = ΔH - TΔS the slope should be -ΔS. When I plotted it, the slope came out as -33.54 so this is equal to -ΔS hence ΔS is 33.54, same as calculated above.

Offline plasticfood

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Re: solubility solve for ksp
« Reply #21 on: November 13, 2011, 10:09:27 PM »
ok thanks again for helping me out!!

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