Question

In the following reactions, identify the oxidising agent and the reducing agent.
$4HCl+Mn{O}_2\to MnC{l}_2+2H_{2}O+C{l}_2$

• A. $Mn{O}_2\text{acts an reducing agent}HCl\text{acts as an oxidising agent}$
• B. $Mn{O}_2$ acts as both reducing as well oxidising agent
• C. $Mn{O}_2\text{acts as an oxidising agent while}HCl\text{acts as an reducing agent}$
• D. $\text{None of the above}$

Answer 1

The correct option is C $Mn{O}_2\text{acts as an oxidising agent while}HCl\text{acts as an reducing agent}$

$Mn{O}_2+4HCl=MnC{l}_2+C{l}_2+2H_{2}O$
Writing the oxidation numbers on various atoms,
$\stackrel{+4}{Mn}\stackrel{-2}{O_2}+\stackrel{+1}{4H}\stackrel{-1}{Cl}=\stackrel{+2}{Mn}\stackrel{-1}{C{l}_2}+\stackrel{0}{C{l}_2}+\stackrel{+1}{2H_2}\stackrel{-2}{O}$
Oxidation number of $Mn$ from $+4$ to $+2$ i.e., decrease in oxidation number. $Mn{O}_2$ is thus reduced. It acts as an oxidising agent. Oxidation number of $Cl$ changes from $-1$ to $0$, i.e., increase in oxidation number. $HCl$ is thus oxidised. It acts as a reducing agent.