December 06, 2019, 11:28:36 PM
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Topic: Dispersion formula mystery...  (Read 387 times)

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Offline electrogeek

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Dispersion formula mystery...
« on: May 04, 2019, 10:53:01 AM »
Hi everyone,

I have been given the question that I've attached below about the use of the London formula to calculate the energy of interaction. I don't understand why the answer is positive however because I got a value of -8.74 kJ per mole...

Because all the numbers are positive which are going into the formula, the answer has to be negative like what I have calculated? Any help would be great because I've had another question on this formula and the same thing happens there where the answer is given to be positive but I calculate a negative value.

Cheers
« Last Edit: May 04, 2019, 11:15:22 AM by electrogeek »

Offline Borek

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Re: Dispersion formula mystery...
« Reply #1 on: May 05, 2019, 03:40:21 AM »
Perhaps it is a matter of convention - are you asked about energy of interactions, or energy of formation?
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Offline mjc123

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Re: Dispersion formula mystery...
« Reply #2 on: May 07, 2019, 05:46:31 AM »
Since the same symbol V is used in question and answer, it ought to refer to the same thing, and therefore be negative.

Offline electrogeek

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Re: Dispersion formula mystery...
« Reply #3 on: May 09, 2019, 01:59:03 PM »
Thanks for the replies. I will have to ask my lecturer because on some revision problems which are about the same idea the values for V are negative in his mark scheme.

Thanks for checking though - just wanted to make sure there wasn't something that I was missing.

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