HgCl₂ and I₂ both when dissolved in water containing I^- ions the pair of species formed is

(a) HgI₂, ${\mathrm{I}}_3^{-}$                              (b) HgI₂, I^-

(c) ${\mathrm{HgI}}_4^{2-}, {\mathrm{I}}_3^{-}$                             (d) Hg₂I₂, I^-

The incorrect statement regarding the lanthanons is ;

Which one of the following statements is correct when SO₂ is passed through acidified

K₂Cr₂O₇ solution?

1. The solution is decolourized

2. SO₂ is reduced

3. Green Cr₂(SO₄)₃ is formed

4. The solution turns blue

Because of lanthanoid contraction, which of the following pairs of elements have nearly

same atomic radii? (Numbers in the parenthesis are atomic numbers).

1. Ti (22) and Zr (40)

2. Zr (40) and Nb (41)

3. Zr (40) and Hf (72)

4. Zr (40) and Ta (73)

Which of the following processes does not involve oxidation of iron?

1. Rusting of iron sheets

2. Decolourisation of blue CuSO₄ solution by iron

3. Formation of Fe(CO)₅ from Fe

4. Liberation of H₂ from steam by iron a high temperature

The correct electronic configuration of Gadolinium(Atomic number = 64)  is :

1. [Xe]4f⁸6d²                   

2. [Xe]4f⁹5s¹

3. [Xe]4f⁷5d¹6s²                   

4. [Xe]4f⁶5d²6s²

Assuming complete ionisation, same moles of which of the following compounds will

require the least amount of acidified KMnO₄ for complete oxidation?

1. FeSO₄

2. FeSO₃

3. FeC₂O₄

4. Fe(NO₂)₂

The reason for lanthanoid contraction is:

1. Negligible screening effect of 'f' orbitals

2. Increasing nuclear charge

3. Decreasing nuclear charge

4. Decreasing screening effect

A diamagnetic lanthanoid ion among the following is :

(At. numbers:  Ce = 58, Sm = 62, Eu = 63, Yb = 70)

1. Ce²⁺

2. Eu²⁺

3. Sm²⁺

4. Yb²⁺

KMnO₄ can be prepared from K₂MnO₄ as per reaction

$3{\mathrm{MnO}}_4^{2-} + 2{\mathrm{H}}_2\mathrm{O}\rightleftharpoons 2{\mathrm{MnO}}_4^{-} + {\mathrm{MnO}}_2 + 4{\mathrm{OH}}^{-}$

The reaction can go to completion by removing OH^- ions by adding

1. HCl

2. KOH

3. CO₂

4. SO₂