Some Important Compounds of Transition Metals

On oxidation of ${\mathrm{S}}_{\mathrm{2}}{\mathrm{O}}_3^{2-}$ by ${\mathrm{MnO}}_4^{-}$  in neutral aqueous medium, the oxidation number of S would change from:

The number of moles of ${\mathrm{KMnO}}_4$ that will be needed to react with one mole of sulphite ion in acidic solution is:

In the scheme given below, $\mathbf{X}$ and $\mathbf{Y}$, respectively, are

$\text{Metal halide} \stackrel{ \mathrm{aq}. \mathrm{NaOH}}{\to } \text{ White precipitate} \left(\mathrm{P}\right)+ \text{Filtrate} \left(\mathrm{Q}\right)$

$\mathrm{P}\mathbf{ }\mathbf{ }\mathbf{ }\underset{ \mathrm{heat} }{\stackrel{ \mathrm{aq}. {\mathrm{H}}_2{\mathrm{SO}}_4}{\stackrel{{\mathrm{PbO}}_2 (\mathrm{excess}) }{⟶}\mathbf{ }\mathbf{ }}}\mathrm{X} \left(\text{a coloured species in solution}\right)$

$\mathrm{Q} \underset{ \mathrm{warm} }{\stackrel{\mathrm{MnO}(\mathrm{OH}{)}_2, \mathrm{Conc}.{\mathrm{H}}_2{\mathrm{SO}}_4}{⟶}} \mathrm{Y}\left(\text{gives blue-coloration with} \mathrm{KI}-\text{starch paper}\right)$

Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox Titration. Some half  cell reactions and their standard potential are given below:

$$\begin{gathered} {\mathrm{MnO}}_4^{-}\left(\mathrm{aq}\right)+8{\mathrm{H}}^{+}\left(\mathrm{aq}\right)+5{\mathrm{e}}^{-}\stackrel{}{\to }{\mathrm{Mn}}^{2+}\left(\mathrm{aq}\right)+4{\mathrm{H}}_2\mathrm{O} {\mathrm{E}}_{}^{\mathrm{o}}=1.51 \mathrm{V} \\ {\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}\left(\mathrm{aq}\right)+14{\mathrm{H}}^{+}\left(\mathrm{aq}\right)+6{\mathrm{e}}^{-}\stackrel{}{\to }2{\mathrm{Cr}}^{3+}\left(\mathrm{aq}\right)+7{\mathrm{H}}_2\mathrm{O} {\mathrm{E}}_{}^{\mathrm{o}}=1.38 \mathrm{V} \\ {\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right) +{\mathrm{e}}^{-}\stackrel{}{\to }{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right) {\mathrm{E}}_{}^{\mathrm{o}}=0.77 \mathrm{V} \\ {\mathrm{Cl}}_2\left(\mathrm{g}\right)+2{\mathrm{e}}^{-}\stackrel{}{\to }2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right) {\mathrm{E}}_{}^{\mathrm{o}}=1.40 \mathrm{V} \end{gathered}$$

Identify the only incorrect statement  regarding the quantitative estimation of aqueous $\mathrm{Fe}{\left({\mathrm{NO}}_3\right)}_2$

The following steps are involved in the manufacturing of potassium dichromate:

What is the difference in the oxidation number of $\mathrm{Cr}$ between X and Y?

In which reaction no colour change will be observed?

Write the Physical Properties of Copper Oxide or Cupric Oxide.

Write a balanced chemical equation for the following word equation:

$\mathrm{Copper}+\mathrm{oxygen}\to \mathrm{copper}\left(\mathrm{II}\right)\mathrm{oxide}$

Dilute nitric acid on reaction with silver liberates ${\mathrm{N}}_2$ gas.

Dilute nitric acid on reaction with silver liberates:

Silver metal reacts with hot concentrated nitric acid and produce silver nitrate $\left({\mathrm{AgNO}}_3\right)$ salt, nitrogen dioxide $\left({\mathrm{NO}}_2\right)$ gas and water as products.

What happens when silver reacts with Hot Conc. ${\mathrm{HNO}}_3$.

In the reaction $2\mathrm{Ag}+2{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Ag}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{SO}}_2$, sulphuric acid acts as an acid as well as an oxidant.

In the reaction $2\mathrm{Ag}+2{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Ag}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{SO}}_2$, sulphuric acid acts as :

The black coating in silver is due to the formation of silver sulphide.

Why is there a black coating in silver?

Silver articles become black on prolonged exposure to air. This is due to the formation of silver sulphide.