which of the following is a redox reaction ?

Options

A. ` Mg(OH)_2 + 2NH_4Cl rarr MgCl_2 + 2NH_4OH`
B. ` Zn+ 2 AgCN rarr 2Ag+ Zn(CN)_2`
C. `CaC_2O_4 + 2HCl rarr CaCl_2 + H_2C_2O_4`
D. `NaCl +KNO_3 rarr NaNO_3 + KCl`

Answer

B

Explanation

It is a redox reaction as `Zn` is oxidized to ` Zn^(2+)` while ` Ag^(+)` is reduced to Ag.
Reactions (1) and (3) are displacement reactions. In the former, a stronger base displaces the weaker base while in the latter a stronger acid displaces the weaker acid. Reaction (4) is a double desplacement reaction.