An example of a reversible reaction is

Options

A. `2Na(s)+H_2O(l)rarr2NaOH(aq.)+H_2(g)`
B. `AgNO_3(aq.)+HCl(aq.)rarrAgCl(s)+HNO_3(aq.)`
C. `KNO_3(aq.)+NaCl(aq.)rarrKCl(aq.)+NaNO_3(aq.)`
D. `Pb(NO_3)_2(aq.)+2NaI(aq.)rarrPbI_2(s)+2NaNO_3(aq.)`

Answer

C

Explanation

In the third reaction, all the reactants and products are water-soluble strong electrolytes. They exists in the form of ions only, which can be exchanged in the forward as well as in the backward direction. Reaction (1) is not reversible because `H_2` is neutral and, hence, cannot react with `NaOH` which is a base. Moreover, `H_2(g)` cannot reduce `Na^(+)` ions. Reactions (2) and (4) are not reversible because one of the products is insoluble in water and, hence, cannot participate in the reverse reaction.