Question:
The incorrect statement(s) among (1) - (3) is (are):
(a) $\mathrm{W}(\mathrm{VI})$ is more stable than $\mathrm{Cr}(\mathrm{VI})$.
(b) in the presence of $\mathrm{HCl}$, permanganate titrations provide satisfactory results.
(c) some lanthanoid oxides can be used as phosophorus.
Correct Option: , 3
Solution:
(i) $\mathrm{W}(\mathrm{VI})$ is more stable than $\mathrm{Cr}(\mathrm{VI})$ due to smaller size of atoms and also due to lanthanide contraction.
(ii) Permanganate titrations in presence of $\mathrm{HCl}$ are unsatisfactory as $\mathrm{HCl}$ is oxidised to $\mathrm{Cl}_{2}$.
(iii) Lanthanoid oxides are used as phosphors.
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