Question
The correct statement(s) about Mössbauer spectroscopy of iron compounds is(are)
Mössbauer Spectroscopy: Correct Statements Analysis
This section analyzes the provided statements regarding Mössbauer spectroscopy of iron compounds to identify the correct ones.
Statement Analysis
- Statement A: '$^{57}Co$' is used as a source
Correct. The radioactive isotope '$^{57}Co$' is the standard precursor source material. It decays to the excited state of '$^{57}Fe$', which subsequently emits the 14.4 keV gamma ray crucial for Mössbauer spectroscopy. - Statement B: Spectra obtained using $\gamma$-ray with resonance energy of 14.4 keV
Correct. Mössbauer spectroscopy relies on the resonant absorption of gamma rays. For iron studies, the specific 14.4 keV gamma ray emitted by '$^{57}Fe$' (following '$^{57}Co$' decay) is utilized. - Statement C: '$K_2[Fe(CN)_5NO]$' shows large quadrupole splitting
Correct. The compound Potassium hexacyanoferrate(II) nitroso, '$K_2[Fe(CN)_5NO]$', contains iron in the +2 oxidation state coordinated with ligands like cyanide (CN⁻) and nitroso (NO⁻). The asymmetric electronic environment caused by these ligands, particularly the strong $\pi$-accepting nature, leads to a significant electric field gradient at the nucleus, resulting in a large quadrupole splitting. - Statement D: Isomer shift of '$FeSO_4 \cdot 7H_2O$' is smaller than '$K_3[Fe(CN)_6]$'
Incorrect. '$FeSO_4 \cdot 7H_2O$' contains iron in the +2 oxidation state (Fe(II)), while '$K_3[Fe(CN)_6]$' contains iron in the +3 oxidation state (Fe(III)). Generally, the isomer shift ( $\delta$ ) decreases as the oxidation state increases. This is because higher oxidation states involve less electron density at the nucleus, leading to a smaller shift. Therefore, the isomer shift of Fe(II) in '$FeSO_4 \cdot 7H_2O$' is typically *larger* than that of Fe(III) in '$K_3[Fe(CN)_6]$'.
Conclusion
Based on the analysis, statements A, B, and C are correct descriptions related to Mössbauer spectroscopy of iron compounds.
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Important Questions from Spectroscopy
- If a molecule emitting a radiation of frequency $3.100 \times 10^9 \text{ Hz}$ approaches an observer with a relative speed of $5.000 \times 10^6 \text{ m s}^{-1}$, then the observer detects a frequency of ________ $\times 10^9 \text{ Hz}$. (rounded off to three decimal places)
[Given: Speed of light $c = 3.000 \times 10^8 \text{ m s}^{-1}$] Consider the following six vibrational modes:
symmetric stretching of $CO_2$, O-H symmetric stretching of $H_2O$, stretching of HCl, stretching of $H_2$, N-H symmetric stretching of $NH_3$, and bending of $CO_2$.
Among these modes, if k number of modes are IR active but Raman inactive, l number of modes are IR inactive but Raman active, and m number of modes are both IR and Raman active.
k, l, and m, respectively, are- The frequency of radiation (in cm$^{-1}$ units) required to vibrationally excite the molecule from v = 0 to v = 1 state is
- The frequency of radiation (in cm$^{-1}$ units) required to rotationally excite the molecule from J = 0 to J = 1 state is
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