Name the gas that can readily decolourise acidified KMnO₄ solution.

(1) CO₂           

(2) SO₂           

(3) NO₂             

(4) P₂O₅

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

1. [Xe]4f⁸6d²                   

2. [Xe]4f⁹5s¹

3. [Xe]4f⁷5d¹6s²                   

4. [Xe]4f⁶5d²6s²

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 that 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

Which of the following species is colourless?

1. ${\mathrm{TiF}}_6^{2-}$ and ${\mathrm{CoF}}_6^{3-}$ 

2. Cu₂Cl₂  and ${\mathrm{NiCl}}_4^{2-}$

3. ${\mathrm{TiF}}_6^{2-}$ and Cu₂Cl₂ 

4. ${\mathrm{CoF}}_6^{3-}$ and ${\mathrm{NiCl}}_4^{2-}$ 

In which of the following pairs are both the ions coloured in aqueous solution?

(1) Ni²⁺, Ti³⁺             

(2) Sc³⁺, Ti³⁺

(3) Sc³⁺, Co²⁺           

(4) Ni²⁺, Cu⁺

(At. no : Sc =21, Ti = 22, Ni = 28, Cu = 29, Co = 27)

HgCl₂ and I₂ both, when dissolved in water containing ${\mathrm{I}}^{-}$ ions the pair of species formed is:

1. ${\mathrm{HgI}}_2,$ ${\mathrm{I}}^{-}$

2. ${\mathrm{HgI}}_4^{2-},$ ${\mathrm{I}}_3^{-}$

3. ${\mathrm{Hg}}_2{\mathrm{I}}_2,$ ${\mathrm{I}}^{-}$

4. ${\mathrm{HgI}}_2,$ ${\mathrm{I}}_3^{-}$

Zinc can be coated on iron to produce galvanised iron, but the reverse is not possible because: