Question

\Lambdan cxample of reversible reaction is (1) $\mathrm{\Lambda }{\mathrm{gNO}}_3(\mathrm{aq})+\mathrm{NaCl}(\mathrm{aq})\to \mathrm{\Lambda }\mathrm{gCl}(\mathrm{s})+{\mathrm{NaNO}}_3(\mathrm{aq})$ (2) $2\mathrm{Na}+2{\mathrm{II}}_2\mathrm{O}\to 2\mathrm{NaOII}+{\mathrm{II}}_2$ (3) $\mathrm{NaOII}+{\mathrm{CII}}_3\mathrm{COOII}\to {\mathrm{CII}}_3\mathrm{COONa}+{\mathrm{II}}_2\mathrm{O}$ (4) $\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2+2\mathrm{NaI}\to {\mathrm{PbI}}_2+2{\mathrm{NaNO}}_3$

Short answer

None of the given reactions are examples of reversible reactions.

Step-by-step solution

Understand the Reaction Types

Identify which types of reactions are given: precipitation, neutralization, single or double displacement. In reversible reactions, the products can revert back to reactants under the same conditions.

Examine the Given Reactions

Analyze each reaction to see if the products can convert back into the original reactants under the same conditions.

Evaluate Reaction (1)

Reaction (1) \ ${\mathrm{AgNO}}_3(\mathrm{aq})+\mathrm{NaCl}(\mathrm{aq})\to \mathrm{AgCl}(\mathrm{s})+{\mathrm{NaNO}}_3(\mathrm{aq})$ \ is a precipitation reaction where $AgCl$ is a solid and generally does not revert back.

Evaluate Reaction (2)

Reaction (2) \ $2\mathrm{Na}+2{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{NaOH}+{\mathrm{H}}_2$ \ is a single displacement reaction and is not easily reversible under normal conditions.

Evaluate Reaction (3)

Reaction (3) \ $\mathrm{NaOH}+{\mathrm{CH}}_3\mathrm{COOH}\to {\mathrm{CH}}_3\mathrm{COONa}+{\mathrm{H}}_2\mathrm{O}$ \ is a neutralization reaction and is generally not reversible in the same conditions.

Evaluate Reaction (4)

Reaction (4) \ $\mathrm{Pb}({\mathrm{NO}}_3{)}_2+2\mathrm{NaI}\to {\mathrm{PbI}}_2+2{\mathrm{NaNO}}_3$ \ is a precipitation reaction where ${\mathrm{PbI}}_2$, a solid, precipitates out and does not revert back.

Conclusion

None of the given reactions are reversible since they involve the formation of solids or gases that do not easily revert back to their original reactants under the same conditions.

Key concepts

Precipitation Reactions

In a precipitation reaction, two aqueous solutions are mixed, and an insoluble solid, known as a precipitate, forms. This reaction can be represented with general formulas where reactants are in aqueous form and at least one product is a solid. For example, when silver nitrate $({\mathrm{AgNO}}_3)$ reacts with sodium chloride $(\mathrm{NaCl})$, silver chloride $(\mathrm{AgCl})$ precipitates as a solid, and sodium nitrate $({\mathrm{NaNO}}_3)$ remains in solution. This type of reaction is usually not reversible because the solid precipitate forms a lattice structure, making it difficult to go back into the solution. Understanding precipitation reactions is key in various fields such as water treatment and chemical analysis.

Single Displacement Reactions

Single displacement reactions involve one element displacing another in a compound. This can be seen when a more reactive element displaces a less reactive one from its compound, often involving a metal and a salt or acid. A classic example is when sodium $\mathrm{Na}$ reacts with water ${\mathrm{H}}_2\mathrm{O}$ where sodium displaces hydrogen, forming sodium hydroxide $\mathrm{NaOH}$ and releasing hydrogen gas ${\mathrm{H}}_2$. $$(2\mathrm{Na}+2{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{NaOH}+{\mathrm{H}}_2)$$ Single displacement reactions are typically not reversible under standard conditions because the reactivity series of metals means that a less reactive metal won't displace a more reactive one. These reactions are fundamental in processes like metallurgy and manufacturing.

Neutralization Reactions

A neutralization reaction occurs when an acid reacts with a base to form a salt and water. This reaction is particularly important in chemistry and everyday life, like in antacid medicines that neutralize stomach acid. For instance, when sodium hydroxide $\mathrm{NaOH}$ reacts with acetic acid ${\mathrm{CH}}_3\mathrm{COOH}$, they form sodium acetate ${\mathrm{CH}}_3\mathrm{COONa}$ and water ${\mathrm{H}}_2\mathrm{O}$. $$(\mathrm{NaOH}+{\mathrm{CH}}_3\mathrm{COOH}\to {\mathrm{CH}}_3\mathrm{COONa}+{\mathrm{H}}_2\mathrm{O})$$ Neutralization reactions are generally exothermic, releasing heat, and are not reversible in the same conditions because the products do not revert to reactants without an external influence. These reactions are crucial in various applications, including pharmaceuticals and agriculture.

Chemical Equilibrium

Chemical equilibrium refers to a state in a reversible reaction where the rate of the forward reaction equals the rate of the reverse reaction, leading to no net change in the concentrations of reactants and products. At equilibrium, the system is stable, though reactions continue to occur on a microscopic level. For reactions to reach equilibrium, they must be reversible. A classic example is the synthesis of ammonia $({\mathrm{NH}}_3)$ from nitrogen $({\mathrm{N}}_2)$ and hydrogen $({\mathrm{H}}_2)$. $$({\mathrm{N}}_2+3{\mathrm{H}}_2\to 2{\mathrm{NH}}_3)$$ At equilibrium, the amount of $({\mathrm{N}}_2)$, $({\mathrm{H}}_2)$, and $({\mathrm{NH}}_3)$ remains constant. Factors such as temperature, pressure, and concentration changes can shift the equilibrium, as described by Le Chatelier's Principle. Understanding equilibrium is essential in fields ranging from industrial processes to biological systems.