Question

Which of the following is a redox reaction ?

• A. ${ NaCl + KNO3 -> NaNO3 + KCl}$
• B. ${CaC2O4 + 2HCl -> CaCl2 + H2C2O4 }$
• C. ${Mg(OH)2 + 2NH4Cl -> MgCl2 + 2NH4OH }$
• D. ${ Zn + 2AgCN -> 2Ag + Zn(CN)2. }$

Answer 1

The Correct Option is D

To determine which of the given reactions is a redox reaction, we need to understand what a redox (reduction-oxidation) reaction is. A redox reaction is one in which the oxidation states of atoms are changed. This involves the transfer of electrons between substances.

Now, let's analyze each of the given reactions and determine if they involve a change in oxidation states:

1. {NaCl + KNO_3 \rightarrow NaNO_3 + KCl}
   • No changes in oxidation states of Na, Cl, K, or N, which indicates that this is not a redox reaction.
2. {CaC_2O_4 + 2HCl \rightarrow CaCl_2 + H_2C_2O_4}
   • No changes in oxidation states of Ca, Cl, H, or C, which indicates that this is not a redox reaction.
3. {Mg(OH)_2 + 2NH_4Cl \rightarrow MgCl_2 + 2NH_4OH}
   • No changes in oxidation states of Mg, Cl, N, or H, which indicates that this is not a redox reaction.
4. {Zn + 2AgCN \rightarrow 2Ag + Zn(CN)_2}
   • In this reaction, Zn is oxidized from 0 to +2 and Ag is reduced from +1 to 0. Therefore, this is a redox reaction as it involves changes in oxidation states of zinc and silver, with a transfer of electrons.

Thus, the correct reaction representing a redox process is:

{Zn + 2AgCN \rightarrow 2Ag + Zn(CN)_2}

In summary, this redox reaction involves zinc being oxidized and silver being reduced, completing the electron transfer process characteristic of redox reactions.