Chemical Forums

Please login or register.

Login with username, password and session length

Sponsored links

Pages: [1]   Go Down

Author Topic: Is there any differences in melting point/ boiling point between isotopes?  (Read 3311 times)

0 Members and 1 Guest are viewing this topic.

iyc

  • Regular Member
  • ***
  • Mole Snacks: +0/-3
  • Offline Offline
  • Gender: Male
  • Posts: 24
  • I'm a llama!

Is there any differences in m.p./b.p. between 35Cl2 and 37Cl2?

In general, van der Waals' forces between the molecules increase with increasing molecular mass.
But, in the case of isotopes, I don't know whether it is true or not.

As both 35Cl2 and 37Cl2 have the same number of electron, the fluctuation in symmetry of charge cloud will be almost the same, resulting similar strength of instantaneous dipole- induced dipole atrraction. Therefore, I think they will have the same m.p./ b.p.

But this contradicts with that van der Waals' forces between the molecules increase with increasing molecular mass.

Can anybody help?
« Last Edit: August 13, 2006, 06:56:25 PM by iyc »
Logged

Mitch

  • Chemistry Editor
  • Administrator
  • Sr. Member
  • *
  • Mole Snacks: +356/-8
  • Offline Offline
  • Gender: Male
  • Posts: 5070
  • "I bring you peace." -Mr. Burns
    • Chemistry Blog

There will be a slight difference, the lighter isotope will boil at a lower temperature.
Logged
Most Common Suggestions I Make on the Forums.
1. Always start by writing a balanced chemical equation.
2. Don't confuse thermodynamic stability with chemical reactivity.
3. Forum Supports LaTex

iyc

  • Regular Member
  • ***
  • Mole Snacks: +0/-3
  • Offline Offline
  • Gender: Male
  • Posts: 24
  • I'm a llama!

is it due to the slight difference in surface area between the isoptopes?
Logged

Yggdrasil

  • Retired Staff
  • Sr. Member
  • *
  • Mole Snacks: +456/-20
  • Offline Offline
  • Gender: Male
  • Posts: 3059
  • Physical Biochemist

As both 35Cl2 and 37Cl2 have the same number of electron, the fluctuation in symmetry of charge cloud will be almost the same, resulting similar strength of instantaneous dipole- induced dipole atrraction.

I think this explanation is right on and the two isotopes will have the same van der Waals forces between them.  However, I think there will be a slight difference in the thermal energy needed to free the heavier 37Cl2 from the solid and/or liquid phase during the phase change, which accounts for the slight increase in bp/mp.
Logged
Pages: [1]   Go Up
 

Mitch Andre Garcia's Chemical Forums 2003-Present.

Page created in 0.137 seconds with 23 queries.