Answer :
Final answer:
In IR spectroscopy, you would not expect to see an IR band for the symmetric stretch of CO2 in a carbonate salt analysis because it is IR inactive, whereas the asymmetric stretch and bends are IR active and would be seen. IR inactive means there's no change in the dipole moment during vibration. Additional IR bands may appear due to common atmospheric gases and the presence of other functional groups in the sample.
Explanation:
The topic of Infrared (IR) spectroscopy and vibrational modes of molecules. In the analysis of carbonate salts on IR, one should not expect to see a band for the symmetric stretch of carbon dioxide (CO2) because this particular vibration does not result in a change in the dipole moment of the molecule, making it IR inactive.
On the contrary, one would expect to see bands corresponding to the asymmetric stretch and the bending vibrations of CO2 since these modes are IR active because they involve changes in the dipole moment.
Regarding carbon dioxide's vibrational modes, CO2 has three fundamental vibrations: two that are IR active (asymmetric stretch and bends) and one that is Raman active (symmetric stretch). In an IR spectrum, the presence of extraneous gases like oxygen, nitrogen, water, and carbon dioxide from the air can sometimes contribute to unintended bands.
However, the primary focus is on the characteristic IR absorbance bands of the sample being analyzed, which for CO2, would be the asymmetric stretch and the bending vibrations.
The intensity of a carbonyl (C=O) stretch reflected on an IR spectrum can change based on other functional groups present and can be lower in a metal carbonyl complex due to back-bonding. For quantitative analysis using IR spectroscopy, it's important to note that infrared sources are not very powerful, particularly in the far IR range, affecting detection limits.
