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  Column I with Column II and mark the most appropriate option:

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. $\left[Xe\right]4 f^6 5d^{2}6s^2$