[khemauck]

Hi,

I'm calculating the bond force constant of HCl as part of a lab for pchem. I've managed to calculate the reduced mass, and the value I have is 0.9801 amu or 1.62 x 10^27 kg.

However when it comes to the bond force constant I am completely stumped. It asks me 'calculate the bond force constant by substituting the midpoint freq into the expression containing the bond force constant' (k).

My midpoint value is 2890 wavenumbers (cm-1) which I converted into Hz by multipying by 3 x 10^10,
giving me 8.64 x 10^13 Hz.

I now have no idea what to do or which equation to use. This page (http://hyperphysics.phy-astr.gsu.edu/hbase/molecule/vibrot.html) seems to have some clues but I just can't get my head around it.

If anyone could point me in the right direction it would be much appreciated!!

[Corribus]

Hate to just throw up a link, but the appropriate equation to use can be found here:

http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Theory

Although, it can be found in the link you provided as well.

If you have the equilibrium frequency and the reduced mass, you can easily calculate the force constant using the equation that contains only these three variables.

[Big-Daddy]

Think of the bond (best of all in a diatomic) as a vibrating spring with masses on either end (one mass a H atom, the other a Cl atom). If you know some physics, you can derive the formula you need!