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GATE 2024 CY – Question 37

Inorganic Chemistry · Instrumental Methods of Analysis: UV-visible, fluorescence and FT-IR spectrophotometry, NMR and ESR spectroscopy, mass spectrometry, atomic absorption spectroscopy, Mössbauer spectroscopy (Fe and Sn) and X- ray crystallography. Electroanalytical methods – cyclic voltammetry, ion-selective electrodes. Thermo-analytical methods: TGA, DTA and DSC. · 2 marks · Multiple choice

In the EPR spectrum of an aqueous solution of $\mathrm{VOSO_4}$ at room temperature, the total number of hyperfine splitting signals is

  1. 3
  2. 7
  3. 5
  4. 8

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Correct answer: (D) 8

Explanation

**EPR hyperfine splitting.** The vanadyl ion $\text{VO}^{2+}$ has the configuration $d^1$ (V(IV)), so there is **one unpaired electron** and an EPR signal is seen.

The unpaired electron interacts with the nuclear spin of the vanadium nucleus. The natural vanadium isotope $^{51}$V (99.75% abundant) has nuclear spin $I=7/2$.

**Number of hyperfine lines:**
$$2I+1=2\left(\tfrac72\right)+1=\mathbf{8}.$$