The incorrect statement(s) among (1) – (3) is (are):
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.

  1. (b) and (c) only

  2. (a) and (b) only

  3.  (b) only

  4.  (a) only


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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