Identify the redox reactions among the following and determine the oxidizing and reducing agents in them:
$(a) 3HCl_{(aq)} + HNO_{3_{(aq)}} \to Cl_{2_{(g)}} + NOCl_{(g)} + 2H_2O_{(l)}$
$(b) HgCl_{2_{(aq)}} + 2KI_{(aq)} \to HgI_{2_{(s)}} + 2KCl_{(aq)}$
$(c) Fe_2O_{3_{(s)}} + 3CO_{(g)} \xrightarrow{\Delta} 2Fe_{(s)} + 3CO_{2_{(g)}}$
$(a) 3HCl_{(aq)} + HNO_{3_{(aq)}} \to Cl_{2_{(g)}} + NOCl_{(g)} + 2H_2O_{(l)}$
$(b) HgCl_{2_{(aq)}} + 2KI_{(aq)} \to HgI_{2_{(s)}} + 2KCl_{(aq)}$
$(c) Fe_2O_{3_{(s)}} + 3CO_{(g)} \xrightarrow{\Delta} 2Fe_{(s)} + 3CO_{2_{(g)}}$
(A, C) To identify a redox reaction,we check for changes in the oxidation numbers of the elements involved.
$(a) 3HCl + HNO_3 \to Cl_2 + NOCl + 2H_2O$
In this reaction,the oxidation number of $Cl$ increases from $-1$ to $0$ (oxidation),and the oxidation number of $N$ decreases from $+5$ to $+3$ (reduction). Thus,it is a redox reaction. $HCl$ is the reducing agent and $HNO_3$ is the oxidizing agent.
$(b) HgCl_2 + 2KI \to HgI_2 + 2KCl$
In this reaction,the oxidation numbers of all elements $(Hg: +2, Cl: -1, K: +1, I: -1)$ remain unchanged. Thus,it is not a redox reaction.
$(c) Fe_2O_3 + 3CO \to 2Fe + 3CO_2$
In this reaction,the oxidation number of $Fe$ decreases from $+3$ to $0$ (reduction),and the oxidation number of $C$ increases from $+2$ to $+4$ (oxidation). Thus,it is a redox reaction. $CO$ is the reducing agent and $Fe_2O_3$ is the oxidizing agent.
$(a) 3HCl + HNO_3 \to Cl_2 + NOCl + 2H_2O$
In this reaction,the oxidation number of $Cl$ increases from $-1$ to $0$ (oxidation),and the oxidation number of $N$ decreases from $+5$ to $+3$ (reduction). Thus,it is a redox reaction. $HCl$ is the reducing agent and $HNO_3$ is the oxidizing agent.
$(b) HgCl_2 + 2KI \to HgI_2 + 2KCl$
In this reaction,the oxidation numbers of all elements $(Hg: +2, Cl: -1, K: +1, I: -1)$ remain unchanged. Thus,it is not a redox reaction.
$(c) Fe_2O_3 + 3CO \to 2Fe + 3CO_2$
In this reaction,the oxidation number of $Fe$ decreases from $+3$ to $0$ (reduction),and the oxidation number of $C$ increases from $+2$ to $+4$ (oxidation). Thus,it is a redox reaction. $CO$ is the reducing agent and $Fe_2O_3$ is the oxidizing agent.
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Observe the following reactions:
$(i)$ $2 KClO_{3(s)} \xrightarrow{\Delta} 2 KCl_{(s)} + 3 O_{2(g)}$
$(ii)$ $2 H_2O_{2(aq)} \xrightarrow{\Delta} 2 H_2O_{(l)} + O_{2(g)}$
$(iii)$ $AgNO_{3(aq)} + KCl_{(aq)} \longrightarrow AgCl_{(s)} + KNO_{3(aq)}$
$(iv)$ $2 Na_{(s)} + \frac{1}{2} O_{2(g)} \longrightarrow Na_2O_{(s)}$
The number of redox reactions in this list is
$(i)$ $2 KClO_{3(s)} \xrightarrow{\Delta} 2 KCl_{(s)} + 3 O_{2(g)}$
$(ii)$ $2 H_2O_{2(aq)} \xrightarrow{\Delta} 2 H_2O_{(l)} + O_{2(g)}$
$(iii)$ $AgNO_{3(aq)} + KCl_{(aq)} \longrightarrow AgCl_{(s)} + KNO_{3(aq)}$
$(iv)$ $2 Na_{(s)} + \frac{1}{2} O_{2(g)} \longrightarrow Na_2O_{(s)}$
The number of redox reactions in this list is
$H_2S$ ($5$ moles) reacts completely with acidified aqueous potassium permanganate solution. In this reaction,the number of moles of water produced is $x$,and the number of moles of electrons involved is $y$. The value of $(x+y)$ is. . . . . .
$X(aq.) + Na_2O_2 \to Y(aq.) \xrightarrow{BaCl_2} Z \downarrow_{\text{Insoluble in dil. } HCl}$
$X$ and $Y$ are different sodium salts. Then the anion present in the salt $(X)$ is:
$X$ and $Y$ are different sodium salts. Then the anion present in the salt $(X)$ is:
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