Question

Identify the oxidising agent and the reducing agent in the following redox reaction:

$5Cl{O}_3^{-}+3A{s}_2{S}_3+9H_{2}O⟶5{Cl}^{-}+6H^{+}+6H_{2}As{O}_4^{-}+9S\downarrow$

• A. Oxidising agent: $Cl{O}_3^{-}$ ; Reducing agent: $A{s}_2{S}_3$
• B. Oxidising agent: $Cl{O}_3^{-}$ ; Reducing agent: $H_{2}O$
• C. Oxidising agent: $H_{2}O$ ; Reducing agent: $A{s}_2{S}_3$
• D. None of these

Answer 1

Answer: (A)

Oxidising agent: $Cl{O}_3^{-}$ ; Reducing agent: $A{s}_2{S}_3$

The redox reaction :

$5Cl{O}_3^{-}+3A{s}_2{S}_3+9H_{2}O⟶5{Cl}^{-}+6H^{+}+6H_{2}As{O}_4^{-}+9S\downarrow$

The oxidation number of Cl decreases from +5 to -1.

Thus, chlorine is reduced.
Hence, $Cl{O}_3^{-}$ acts as oxidizing agent.

The oxidation number of As increases from +3 to +5.

Thus, As is oxidized.
Hence, $A{s}_2{O}_3$ acts as reducing agent.