Question

$\mathrm{Zn}+\left(\mathrm{dil}.\right){\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{ZnSO}}_4+{\mathrm{H}}_2$

Above reaction is

• A. decomposition reaction
• B. single displacement reaction
• C. oxidation reaction
• D. neutralisation reaction

Answer 1

The correct option is B

single displacement reaction

Explanation for the correct option:

option B

• In a single displacement reaction or displacement reaction, an element from its compound is substituted by another element to form two product species.
• This kind of reaction occurs between an element and a compound. In this type of reaction, an element that is more reactive displaces the element that is comparatively less reactive in nature.
• In the given reaction, the element Zinc $\left(\mathrm{Zn}\right)$ reacts with the compound Sulfuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ to form Zinc sulfate $\left({\mathrm{ZnSO}}_4\right)$ and Hydrogen gas$\left({\mathrm{H}}_2\right)$.
• Hence, the given reaction is classified as a single displacement reaction.

$\mathrm{Zn}\left(\mathrm{s}\right)+\left(\mathrm{dil}.\right){\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

Explanation for the incorrect options:

option A

• The reaction in which either two or more products are formed from a single reactant substance is termed a decomposition reaction.
• Example, Calcium carbonate or Limestone $\left({\mathrm{CaCO}}_3\right)$ decomposes to form Calcium oxide or Quicklime $\left(\mathrm{CaO}\right)$ and Carbon dioxide $\left({\mathrm{CO}}_2\right)$in the presence of heat.

${\mathrm{CaCO}}_3\left(\mathrm{s}\right)\stackrel{∆}{\to }\mathrm{CaO}+{\mathrm{CO}}_2$

• Due to the presence of two reactant species$\left(\mathrm{Zn}\mathrm{and}{\mathrm{H}}_2{\mathrm{SO}}_4\right)$, the given reaction is not classified as a decomposition reaction.

option C

• Oxidation reaction is accompanied by the increase in the oxidation state while reduction reaction is accompanied by the decrease in the oxidation state.
• The reaction in which oxidation and reduction reactions take place simultaneously is known as redox reactions.
• The oxidation state of Zinc $\left(\mathrm{Zn}\right)$ changes from zero in $\mathrm{Zn}$ to +2 in${\mathrm{ZnSO}}_4$, hence it is undergoing oxidation. Whereas, the oxidation state of Hydrogen $\left(\mathrm{H}\right)$ changes from +1 in${\mathrm{H}}_2{\mathrm{SO}}_4$ to zero in${\mathrm{H}}_2$, hence it is undergoing reduction.
• Since reduction and oxidation take place simultaneously, the given reaction is a redox reaction and not an oxidation reaction.

option D

• The reaction in which acid and base react with each other for the formation of salt and water is termed a neutralization reaction.
• For example, the reaction between Hydrochloric acid or Hydrogen chloride $\left(\mathrm{HCl}\right)$ and Sodium hydroxide or Caustic soda $\left(\mathrm{NaOH}\right)$ to form salt Sodium chloride $\left(\mathrm{NaCl}\right)$ and Water$\left({\mathrm{H}}_2\mathrm{O}\right)$.

$\mathrm{HCl}\left(\mathrm{aq}\right)+\mathrm{NaOH}\left(\mathrm{aq}\right)\to \mathrm{NaCl}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

• Since Sulfuric acid is an acid but Zinc is not a base, the given reaction can not be classified as a neutralization reaction.

Hence, option B is correct. Given reaction is a single displacement reaction.