The yellow colour solution of ${\mathrm{Na}}_2{\mathrm{CrO}}_4$ changes to orange-red on passing ${\mathrm{CO}}_2$ gas due to the formation of :

(1) ${\mathrm{CrO}}_5$                                         

(2) ${\mathrm{CrO}}_3$

(3) ${\mathrm{Na}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$                                 

(4) ${\mathrm{Cr}}_2{\mathrm{O}}_3$

${\mathrm{FeCr}}_2{\mathrm{O}}_4+4{\mathrm{Na}}_2{\mathrm{CO}}_3+{\mathrm{O}}_2\stackrel{\mathbf{Fusion}}{\to }\left[\mathbf{X}\right]\underset{ \mathbf{ }\mathbf{ }{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{ } }{\overset{{\mathbf{H}}^{\mathbf{+}}}{\to }}\left[\mathbf{Y}\right]\underset{{\mathbf{H}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{2}}}{\overset{{\mathbf{H}}^{\mathbf{+}}}{\to }}\left[\mathbf{Z}\right]$

Which of the following statements is true for the compounds [X], [Y] and [Z] ?

${\mathrm{KMnO}}_4$ on treatment with conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$ forms a compound (X) which decomposes explosively on heating forming (Y). The (X) and (Y) are respectively :

(A) ${\mathrm{Mn}}_2{\mathrm{O}}_7, {\mathrm{MnO}}_2$                                       

(B) ${\mathrm{Mn}}_2{\mathrm{O}}_7, {\mathrm{Mn}}_2{\mathrm{O}}_3$

(C) ${\mathrm{MnSO}}_4, {\mathrm{MnO}}_2$                                       

(D) ${\mathrm{Mn}}_2{{\mathrm{O}}_3}^{-}, {{\mathrm{MnO}}_4}^{2-}$

Which of the following products are formed when potassium bromide reacts with potassium permanganate in alkaline pH?

1. ${{\mathrm{BrO}}_3}^{‐}, {\mathrm{MnO}}_2$                                     

2. ${{\mathrm{BrO}}_4}^{‐}, {\mathrm{Mn}}^{2+}$

3. ${\mathrm{Br}}_2, {\mathrm{MnO}}_2$                                         

4. ${\mathrm{Br}}_2{\mathrm{O}}^{‐}, {{\mathrm{MnO}}_4}^{2‐}$

Assertion : The number of unpaired electrons in the following gaseous ions:

                   ${\mathrm{Mn}}^{3+}, {\mathrm{Cr}}^{3+}, {\mathrm{V}}^{3+} \mathrm{and} {\mathrm{Ti}}^{3+}$are 4, 3, 2 and 1 respectively

Reason : ${\mathrm{Cr}}^{3+}$ is stable in aqueous solution.

Assertion : Cuprous ion $\left({\mathrm{Cu}}^{+}\right)$ is colourless whereas cupric ion $\left({\mathrm{Cu}}^{2+}\right)$ produces blue colour in solution.

Reason : Cuprous ion $\left({\mathrm{Cu}}^{+}\right)$ has unpaired electrons while cupric ion $\left({\mathrm{Cu}}^{2+}\right)$ does not.

Assertion : Ammonical silver nitrate converts glucose to gluconic acid and metallic silver is precipitated.

Reason : Glucose acts as a weak reducing agent.

Assertion: To a solution of potassium chromate if a strong acid is added it changes its colour from yellow to orange.

Reason : The colour change is due to the oxidation of potassium chromate.

Which one of the following statements is not correct

1. Nickel forms Ni(CO)₄

2. All the transition metals form mono-metallic carbonyls

3. Carbonyl are formed by transition metals

4. Transition metals form complexes

Which of the following pairs of compounds are more stable

(A) $K_2\left[NiC{l}_6\right],\left[Pt\right(CN{)}_4{]}^{2-}$

(B) NiCl₄, PtCl₄

(C) $\left[Ni\right(CN{)}_4{]}^{2-}, K_2\left[Pt\right(C{l}_6\left)\right]$

(D) PtCl₂, NiCl₂