Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions:

Question:

Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions:

(a) $2 \mathrm{AgBr}(\mathrm{s})+\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{O}_{2}(\mathrm{aq}) \rightarrow 2 \mathrm{Ag}(\mathrm{s})+2 \mathrm{HBr}(\mathrm{aq})+\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{O}_{2}(\mathrm{aq})$

(b) $\mathrm{HCHO}(\mathrm{I})+2\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right]^{+}(\mathrm{aq})+3 \mathrm{OH}^{-}(\mathrm{aq}) \rightarrow 2 \mathrm{Ag}(\mathrm{s})+\mathrm{HCOO}^{-}(\mathrm{aq})+4 \mathrm{NH}_{3}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{I})$

(c) $\mathrm{HCHO}(\mathrm{I})+2 \mathrm{Cu}^{2+}(\mathrm{aq})+5 \mathrm{OH}^{-}(\mathrm{aq}) \rightarrow \mathrm{Cu}_{2} \mathrm{O}(\mathrm{s})+\mathrm{HCOO}^{-}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

(d) $\mathrm{N}_{2} \mathrm{H}_{4}(\mathrm{I})+2 \mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{I}) \rightarrow \mathrm{N}_{2}(\mathrm{~g})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{I})$

(e) $\mathrm{Pb}(\mathrm{s})+\mathrm{PbO}_{2}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \rightarrow 2 \mathrm{PbSO}_{4}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

 

Solution:

(a) Oxidised substance $\rightarrow \mathrm{C}_{6} \mathrm{H}_{6} \mathrm{O}_{2}$

Reduced substance $\rightarrow \mathrm{AgBr}$

Oxidising agent $\rightarrow \mathrm{AgBr}$

Reducing agent $\rightarrow \mathrm{C}_{6} \mathrm{H}_{6} \mathrm{O}_{2}$

(b)Oxidised substance $\rightarrow \mathrm{HCHO}$

Reduced substance $\rightarrow\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right]^{+}$

Oxidising agent $\rightarrow\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right]^{+}$

Reducing agent $\rightarrow \mathrm{HCHO}$

(c) Oxidised substance $\rightarrow \mathrm{HCHO}$

Reduced substance $\rightarrow \mathrm{Cu}^{2+}$

Oxidising agent $\rightarrow \mathrm{Cu}^{2+}$

Reducing agent $\rightarrow \mathrm{HCHO}$

(d) Oxidised substance $\rightarrow \mathrm{N}_{2} \mathrm{H}_{4}$

Reduced substance $\rightarrow \mathrm{H}_{2} \mathrm{O}_{2}$

Oxidising agent $\rightarrow \mathrm{H}_{2} \mathrm{O}_{2}$

Reducing agent $\rightarrow \mathrm{N}_{2} \mathrm{H}_{4}$

(e) Oxidised substance $\rightarrow \mathrm{Pb}$

Reduced substance $\rightarrow \mathrm{PbO}_{2}$

Oxidising agent $\rightarrow \mathrm{PbO}_{2}$

Reducing agent $\rightarrow \mathrm{Pb}$

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