Question

Given below are two statements:
Statement I: The number of paramagnetic species among $[\mathrm{CoF_6}]^{3-}$, $[\mathrm{TiF_6}]^{3-}$, $\mathrm{V_2O_5}$ and $[\mathrm{Fe(CN)_6}]^{3-}$ is 3.
Statement II: $ \mathrm{K_4[Fe(CN)_6]}<\mathrm{K_3[Fe(CN)_6]}<\mathrm{[Fe(H_2O)_6]SO_4 \cdot H_2O}<\mathrm{[Fe(H_2O)_6]Cl_3} $ is the correct order in terms of number of unpaired electrons.
Choose the correct answer from the options given below:

• A. Both Statement I and Statement II are false
• B. Statement I is false but Statement II is true
• C. Statement I is true but Statement II is false
• D. Both Statement I and Statement II are true
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Hint:

Strong field ligands like CN$^-$ cause electron pairing, while weak field ligands like H$_2$O increase paramagnetism.

Answer 1

The Correct Option is D

Step 1: Analysis of Statement I.
$[\mathrm{CoF_6}]^{3-}$ is high spin and paramagnetic.
$[\mathrm{TiF_6}]^{3-}$ contains one unpaired electron and is paramagnetic.
$\mathrm{V_2O_5}$ contains unpaired electrons and is paramagnetic.
$[\mathrm{Fe(CN)_6}]^{3-}$ is low spin due to strong field ligand CN$^-$ and has unpaired electrons.
Hence, three species are paramagnetic. Statement I is true.
Step 2: Analysis of Statement II.
CN$^-$ is a strong field ligand causing pairing of electrons, while H$_2$O is a weak field ligand causing maximum unpaired electrons.
Thus, the given increasing order of unpaired electrons is correct.
Step 3: Conclusion.
Both Statement I and Statement II are correct.