From the following, which is the most basic hydroxide?

1. Ce(OH)₃

2. Lu(OH)₃

3. Yb(OH)₃

4. Tb(OH)₃

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.

A pair among the following that have the same size is:

1. Fe³⁺, Ni²⁺

2. Zr⁴⁺, Ti⁴⁺

3. Zr⁴⁺ , Hf⁴⁺

4. Zn²⁺, Hf⁴⁺

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 ${\mathrm{NiCl}}_4^{2-}$ 

Find the main reason responsible for actinide contraction.
1. Poor shielding by the 5f subshell
2. Extraordinary decrement in Z_eff
3. Both (1) and (2)
4. Strong shielding by the 5f subshell

At pH = X, \(\text{CrO}_4^{2-}\)​ (yellow) changes to \(\text{Cr}_2\text{O}_7^{2-}\) (orange), and vice versa at pH = Y.
What are the values of X and Y, respectively?

1. 6, and 8

2. 6, and 5

3. 8, and 6

4. 7, and 7

When iron becomes passive by "X", it is due to the formation of "Y". X and Y, respectively, are:

1. Dil. HCl, ${\mathrm{Fe}}_2{\mathrm{O}}_3$

2. 80% Conc. ${\mathrm{HNO}}_3$, ${\mathrm{Fe}}_3{\mathrm{O}}_4$

3. Conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$, ${\mathrm{Fe}}_3{\mathrm{O}}_4$

4. Conc. HCl, ${\mathrm{Fe}}_3{\mathrm{O}}_4$

When KMnO₄ solution is added to hot oxalic acid solution, the decolorization is slow in the beginning but becomes instantaneous after some time. This is because : 

1. ${\mathrm{Mn}}^{2+}$ acts as auto catalyst.

2. ${\mathrm{CO}}_2$ is formed.

3. Reaction is exothermic.

4. ${\mathrm{MnO}}_4^{-}$ catalyses the reaction.