Which of the following is a redox reaction

• Redox Electrochemistry

Which of the following is a redox reaction?

1. NaCl + KNO₃ → NaNO₃ + KCl
2. Mg(OH)₂ + 2NH₄Cl → MgCl₂ + 2NH₄OH
3. CaC₂O₄ + 2HCl → CaCl₂ + H₂C₂O₄
4. 2Zn + 2AgCN → 2Ag + Zn(CN)₂

Answer

In all the three reaction there is no change in the oxidation states. These are simple inonic reactions.

But in 2Zn + 2AgCN → 2Ag + Zn(CN)₂ there is a change in oxidation state. Ag gains electrons and Zn lose electrons therefore it is a redox reaction.

The correct option is D.