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:

Identify the incorrect statements related to lanthanons:
 

The reason for a greater range of oxidation states in actinoids is attributed to:

1. Actinoid contraction

2. 5f, 6d and 7s levels having comparable energies.

3. 4f and 5d levels being close in energies.

4. The radioactive nature of actinoids

Match the metal ions given in Column I with the spin magnetic moments of the ions given in Column II
and select  the correct match:

When copper is heated with conc. HNO₃ it produces:

1. Cu(NO₃) and NO

2. Cu(NO₃)₂, NO and NO₂

3. Cu(NO₃)₂ and N₂O

4. Cu(NO₃)₂ and NO₂

SO₂ is passed through an acidified K₂Cr₂O₇ solution.
The correct statement among the following regarding the above experiment is:

1. The solution gets decolorized.

2. SO₂ gets reduced.

3. Green coloured Cr₂(SO₄)₃ gets formed.

4. The solution turns blue.

Gadolinium belongs to 4f series. It’s atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?

1. $\left[Xe\right]4 f^8 6d^2$

2. $\left[Xe\right]4 f^9 5s^1$

3. $\left[Xe\right]4 f^7 5d^{1}6s^2$

4. $\left[Xe\right]4 f^6 5d^{2}6s^2$