Question

An example of reversible reaction is:

• A. $Pb{\left({NO}_3\right)}_2+2NaI\to Pb{I}_2+2Na{NO}_3$
• B. $Ag{NO}_3+HCl=AgCl+H{NO}_3$
• C. $2Na+2H_{2}O=2NaOH+H_2$
• D. $K{NO}_3+NaCl=KCl+Na{NO}_3$

Answer 1

Answer: (A), (D)

The correct options are
A $Pb{\left({NO}_3\right)}_2+2NaI\to Pb{I}_2+2Na{NO}_3$
D $K{NO}_3+NaCl=KCl+Na{NO}_3$

• In reaction B, due to the formation of stable precipitate $AgCl$, the reaction is stabilised and is irreversible.
• In reaction C, $H_2$ gas is liberated which is no more present in the reacting system, as a result the reaction does not go in the reverse direction and it is irreversible.
• In reaction A, the products $Pb{I}_2$ and $2NaN{O}_3$ react readily to give the reactants again as $Pb{I}_2$ is highly unstable. As a result the reaction is reversible.
• In reaction D, K and Na have close reactivities, therefore, they displace each other readily both on the reactant as well as on the product side. Thus, making the reaction reversible.