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^-

Which one of the following statements related to lanthanons is incorrect?

(1) Europium shows +2 oxidation state

(2) The basicity decreases as the ionic radius decreases from Pr to Lu

(3) All the lanthanons are much more reactive than aluminium

(4) Ce (+4) solutuion are widely used as oxidising agent in volumetric analysis

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

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⁺

Among the following, the incorrect statement regarding interstitial compounds is:

1. They retain metallic conductivity.

2. They are chemically reactive.

3. They are much harder than the pure metal.

4. They have higher melting points than the pure metal.

Identify the mixture of metals which contain a non-metal as a constituent in it.

1. lnvar

2. Steel

3. Bell metal

4. Bronze

Which of the statements is not true?

1. On passing H₂S through acidified K₂Cr₂O₇ solution, a milky colour is observed

2. Na₂Cr₂O₇ is preferred over K₂Cr₂O₇ in volumteric analysis

3. K₂Cr₂O₇ solution in acidic medium is orange

4. K₂Cr₂O₇ solution becomes yellow on increasing the pH beyond 7