JUNE 2024 — Chemistry STD 12 Science — Question

Choose the correct statement($s$) about the above process

$(A)$ $OH ^{-}$ions react with $N _2 H _4$ at the anode to form $N _2( g )$ and water, releasing 4 electrons to the anode.

$(B)$ At the cathode, $N _2 H _4$ breaks to $N _2( g )$ and nascent hydrogen released at the electrode reacts with oxygen to form water.

$(C)$ At the cathode, molecular oxygen gets converted to $OH ^{-}$.

$(D)$ Oxides of nitrogen are major by-products of the electrochemical process.

$\mathrm{Cr}_2 \mathrm{O}_7{ }^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-} \rightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_2 \mathrm{O}, \mathrm{E}^{\circ}=1.33 \mathrm{~V}$

$\mathrm{Fe}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \rightarrow \mathrm{Fe}  \mathrm{E}^{\circ}=-0.04 \mathrm{~V}$

$\mathrm{Ni}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \rightarrow \mathrm{Ni}  \mathrm{E}^{\circ}=-0.25 \mathrm{~V}$

$\mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{e}^{-} \rightarrow \mathrm{Ag} \mathrm{E}^{\circ}=0.80 \mathrm{~V}$

$\mathrm{Au}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \rightarrow \mathrm{Au} \mathrm{E}^{\circ}=1.40 \mathrm{~V}$

Consider the given electrochemical reactions, The number of metal$(s)$ which will be oxidized be $\mathrm{Cr}_2 \mathrm{O}_7{ }^{2-}$, in aqueous solution is. . . . . .