The Naked Scientists

The Naked Scientists Forum

Author Topic: What determines whether a molecule is more likely to form dimers?  (Read 5339 times)

Offline 113zami

  • Jr. Member
  • **
  • Posts: 11
    • View Profile
this question has confused me for a long time, please help

4)which molecule is likely to form dimers?

a)BF3
b)NO2-
c)NO2
d)NO2+

the correct answer is  C   , C is a radicle and I can uderstand why it would form dimers but why wouldn't the other choices be able to form dimers?, to my knowledge any 2 molecules can form dimers there isn't really a restriction to forming dimers

thanks

« Last Edit: 22/06/2008 10:29:37 by chris »


 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8645
  • Thanked: 42 times
    • View Profile
Well, 2 of them are charged and if you tried to stick pairs of them together the charges would repel.
BF3 may well form a dimer at very low temperatoures and pressures (as do some of the inert gases) so you have a valid point. However, putting that answer in an exam mihght not help you much.

BF3 is a much more interesting question- BH3 certainly does form a dimer.
I presume it's because the electron withdrawing nature of the fluorines means that there's not much electron density on the boron to do any bonding. That is certainly why it's a strong lewis acid
http://en.wikipedia.org/wiki/Lewis_acid

Anyway, well done for asking an interesting question.
 

Offline 113zami

  • Jr. Member
  • **
  • Posts: 11
    • View Profile
thank you very much
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length