chem question help please

hi, please could I have help with querstion 3aiv of this paper: https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FChemistry%2FA-level%2FPast-Papers%2FCAIE%2FPaper-2%2FQP%2FNovember%202019%20(v1)%20QP.pdf
How is infrared going to help? The ms says compare the wavelengths but how does that indicate the levels?
thanks!

A level doesn’t really explain this, but each bond can undergo stretches that have characteristic frequencies which allow you to positively identify them.
Starting from the equation c = fλ, we find that f/c = 1/λ, where 1/λ (the reciprocal of the wavelength) is the wavenumber range, f is the frequency and c is the speed of light in a vacuum.
This result shows how the frequency of the stretches etc impacts the wavenumber ranges at which you get absorbance peaks on an IR spectrum.
You may also be aware of a couple of equations from simple harmonic motion, including
f = 1/(2π) x √(k/m)
You can use this very simplistic model to comment that the “stiffness” of the bond also is important in determining the frequency of oscillation and therefore the wavenumber ranges observed. There are better models to use, but these are more advanced and offer no real benefit to cover.
So carbon monoxide can be monitored using IR spectroscopy since the bond has a very characteristic stretching vibration and an IR spectrum should pick up on whether this vibration is observed.
Mass spec wouldn’t work too well, since CO and N2 have the same Mr and thus you’d get a lot of confusion. 13C NMR wouldn’t work too well, since you’d need to dissolve a lot of CO in the air first in order to get a decent spectrum and this isn’t super easy to do.