[NotSoSure]

hey I have tried to solve this:

The 12Carbon-14Nitrogen triple bond absorbs energy at 2150cm-1. How much shift do we expect in the peak of the Carbon-Nitrogen infrared spectrum, when we replace the 14Nitrogen atom with 15Nitrogen?

I did: ν=1/2π√k/μ => μ1=mC*mN(14)/mC+mN14 , μ2=mC*mN(15)/mC+mN15 then Δν=ν2-ν1. Is this correct?
I ask because it gives data: Avogadro constant (NA), Planck constant (h), (c) velocity and says k stays the same. I didn't use Avogadro constant anywhere..neither 2150cm-1. Any help? Thanks:)

[mjc123]

You don't need the constants, all you need is the ratio of the reduced masses.

[NotSoSure]

Thank you for your reply! Is the way I solved it correct?

[mjc123]

You haven't solved it, but your approach is along the right lines.

[NotSoSure]

For masses I'll put mC=12 and m14N=14 , m15N=15 then replace the data given on those equations. Is there anything else I'm missing? Thank you for replying!!

[sjb]

m14N is not 14, and m15N  is not 15 if we are going to be picky (but probably won't make much difference)