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4. d and f- block elements — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistry4. d and f- block elements1 Mark
MCQ
Identify correct statements from below:

$A$. The chromate ion is square planar.

$B$. Dichromates are generally prepared from chromates.

$C$. The green manganate ion is diamagnetic.

$D$. Dark green coloured $\mathrm{K}_2 \mathrm{MnO}_4$ disproportionates in a neutral or acidic medium to give permanganate.

$E$. With increasing oxidation number of transition metal, ionic character of the oxides decreases.

Choose the correct answer from the options given below:

  • A
    $B, C, D$ only
  • B
    $A, D, E$ only
  • C
    $A, B, C$ only
  • ✓
    $B, D, E$ only
✓

Answer

Correct option: D.
$B, D, E$ only
d
$A$. $\mathrm{CrO}_4{ }^{2-}$ is tetrahedral

$B$. $2 \mathrm{Na}_2 \mathrm{CrO}_4+2 \mathrm{H}^{+} \rightarrow \mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_{/}+2 \mathrm{Na}^{+}+\mathrm{H}_2 \mathrm{O}$

$C$. As per $NCERT$, green manganate is paramagnetic with $1$ unpaired electron.

$D$. Statement is correct

$E$. Statement is correct

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