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14
MCQ (Multiple Correct Answer)

The exhibition of various oxidation states by an element is also related to the outer orbital electronic configuration of its atom. Atom (s) having which of the following outermost electronic configurations will exhibit more than one oxidation state in its compounds.

A
$3 s^1$
B
$3 d^1 4 s^2$
C
$3 d^2 4 s^2$
D
$3 s^2 3 p^3$
15
MCQ (Multiple Correct Answer)

Identify the correct statements with reference to the given reaction

$$\mathrm{P}_4+3 \mathrm{OH}^{-}+3 \mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{PH}_3+3 \mathrm{H}_2 \mathrm{PO}_2^{-}$$

A
Phosphorus is undergoing reduction only
B
Phosphorus is undergoing oxidation only
C
Phosphorus is undergoing oxidation as well as reduction
D
Hydrogen is undergoing neither oxidation nor reduction
16
MCQ (Multiple Correct Answer)

Which of the following electrodes will act as anodes, which connected to Standard Hydrogen Electrode ?

A
$\mathrm{Al} / \mathrm{Al}^{3+} \quad E^{\ominus}=-1.66$
B
$\mathrm{Fe} / \mathrm{Fe}^{2+} \quad E^{\ominus}=-0.44$
C
$\mathrm{Cu} / \mathrm{Cu}^{2+} \quad E^{\ominus}=+0.34$
D
$\mathrm{F}_2(\mathrm{~g}) / 2 \mathrm{~F}^{-}(\mathrm{aq}) E^{\ominus}=02.87$
17
Subjective

The reaction $\mathrm{Cl}_2(g)+2 \mathrm{OH}^{-}(a q) \rightarrow \mathrm{ClO}^{-}(a q)+\mathrm{Cl}^{-}(a q)+\mathrm{H}_2 \mathrm{O}(l)$ represents the process of bleaching. Identify and name the species that bleaches the substances due to its oxidising action.

Explanation

$$\mathop {C{l_2}}\limits^0 (g) + \mathop {2O{H^ - }}\limits^{ - 2\,\,\, + 1} (aq) \to \mathop {Cl{O^ - }}\limits^{ + 1\,\,\, - 2} (aq) + \mathop {C{l^ - }}\limits^{ - 1} (aq) + \mathop {{H_2}O}\limits^{ + 1\,\,\,\, - 2} (l)$$

In this reaction, $\mathrm{O} . \mathrm{N}$. of Cl increases from $0\left(\right.$ in $\left.\mathrm{Cl}_2\right)$ to 1 (in $\left.\mathrm{ClO}^{-}\right)$as well as decreases from 0 (in $\mathrm{Cl}_2$ ) to -1 (in $\mathrm{Cl}^{-}$). So, it acts both reducing as well as oxidising agent. This is an example of disproportionation reaction. In this reaction, $\mathrm{ClO}^{-}$species bleaches the substances due to its oxidising action. [In hypochlorite ion $\left(\mathrm{ClO}^{-}\right) \mathrm{Cl}$ can decrease its oxidation number from +1 to 0 or -1 .]

18
Subjective

$\mathrm{MnO}_4^{2-}$ undergoes disproportionation reaction in acidic medium but $\mathrm{MnO}_4^{-}$does not. Give reason.

Explanation

In $\mathrm{MnO}_4^{2-}$, the oxidation number of Mn is +6 . It can increase its oxidation number (to +7 ) or decrease its oxidation number (to $+4,+3,+2,0$ ). Hence, it undergoes disproportionation reaction in acidic medium.

In $\mathrm{MnO}_4^{-}, \mathrm{Mn}$ is in its highest oxidation state, i.e., +7 . It can only decrease its oxidation number. Hence, it cannot undergo disproportionation reaction.