Question

An example of a reversible reaction is:
(A) \[AgN{{O}_ {3}} (aq)+NaCl(aq)\to AgCl(s)+Nan{{O}_ {3}} (aq)\]
(B) \[2Na(s)+2{{H}_ {2}} O(l)\to 2NaOH(aq)+{{H}_{2(g)}} \]
(C) \[2KCl{{O}_ {3}} (s)\to 2KCl(s)+3{{O}_ {2}} (g)\]
(D) \[N{{H}_ {4}} HS(s)\to N{{H}_ {3}} (g)+{{H}_ {2}} S(g)\]

Answer 1

Hint: A reversible reaction is a reaction where the reactants and products react together to give the reactants back. A and B can react to form C and D or, in the reverse reaction, C and D can react to form A and B. This is distinct from reversible processes in thermodynamics.

Complete step by step solution:
We have been provided with 4 chemical equations:
(a) \[AgN{{O}_ {3}} (a)+NaCl(aq)\to AgCl(s)+NaN{{O}_ {3}} (aq)\]
(b) \[2Na(s)+2{{H}_ {2}} O(l)\to 2NaOH(aq)+{{H}_{2(g)}} \]
(c) \[2KCl{{O}_ {3}} (s)\to 2KCl(s)+3{{O}_ {2}} (g)\]
(d) \[N{{H}_ {4}} HS(s)\to N{{H}_ {3}} (g)+{{H}_ {2}} S(g)\]
We need to tell which of them is an example of reversible reaction,
So, for that: we must know about the reversible reaction
In some chemical reactions, the products of the reaction can react together to produce the original reactants. These reactions are called reversible reactions. They can be represented in the following way:
\[A+B\rightleftharpoons C+D\]
In (a) due to the formation of stable precipitate AgCl, the reaction is stabilised and is irreversible.
In (b) ${{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 (c) due to the formation of stable KCl, the reaction is stabilised and is irreversible,
In (d) both the products formed are unstable at lower pressure and react to form the original reactants again, so it is a reversible reaction.
So, we can say that \[N{{H}_ {4}} HS(s)\to N{{H}_ {3}} (g)+{{H}_ {2}} S(g)\]is a reversible reaction,

Therefore, option (D) is correct.

Note: Solid hydrogen sulphide is well known as a typical molecular crystal but its stability under pressure is still under debate. Results show that Solid hydrogen sulphide is stable at lower pressure but decomposes at high pressure.