March 29, 2024, 09:53:54 AM
Forum Rules: Read This Before Posting


Topic: Dispersion formula mystery...  (Read 1444 times)

0 Members and 1 Guest are viewing this topic.

Offline electrogeek

  • Regular Member
  • ***
  • Posts: 31
  • Mole Snacks: +0/-0
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

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27635
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
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?
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 2048
  • Mole Snacks: +296/-12
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

  • Regular Member
  • ***
  • Posts: 31
  • Mole Snacks: +0/-0
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.

Sponsored Links