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.

Which of the following statements is false? 

The addition of non-metals like B and C to the interstitial sites of a transition metal increases

1. Ductility

2. Melting Point

3. Shining

4. Conductivity

Which of the following metals does not form amalgam?

1. Fe

2. Au

3. Zn

4. Ag

The element of the first transition series having lowest oxidation potential value $(\mathrm{M}\to {\mathrm{M}}^{2+}+2{\mathrm{e}}^{-})$ is -

1. Mn

2. Fe

3. Ni

4. Cu

The incorrect statement among the following about the chemistry of 3d and 4f series elements is 

Which of the following elements has the strongest metallic bond?

The ionization potential values of d-block elements as compared to the ionization potential values of f-block elements are:

The incorrect statement among the following regarding Cerium is :