Question

Of the following reactions, only one is a redox reaction. Identify it

• A. $Ca ( OH )_2+2 HCl \longrightarrow CaCl _2+2 H _2 O$
• B. $BaCl _2+ MgSO _4 \longrightarrow BaSO _4+ MgCl _2$
• C. $2 S _2 O _7^{2-}+2 H _2 O \longrightarrow 4 SO _4^{2-}+4 H ^{+}$
• D. $Cu _2 S +2 FeO \longrightarrow 2 Cu +2 Fe + SO _2$

Answer 1

Answer: (D)

In redox reactions oxidation and reduction take place side by side.
$ Cu_2S + 2FeO \rightarrow 2Cu + 2Fe + SO_2$
O.N. of $Cu$ changes from $+1$ to 0 (reduction) and O.N. of $S$ changes from $-2$ to $+4$ (oxidation).