Question

The reaction, $H_2+C{l}_2\to 2HCl$ is

• A. decomposition reaction
• B. displacement reaction
• C. a combination reaction
• D. an isomerization reaction

Answer 1

The correct option is C

a combination reaction

Explanation for the correct option:

(C)

• The reaction in which a single product molecule is formed from the combination of either two or more than two reactant species is termed a combination reaction.
• In the given reaction,
• ${\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)\to 2\mathrm{HCl}\left(\mathrm{g}\right)$.
• Hydrogen $\left({\mathrm{H}}_2\right)$ and Chlorine molecule $\left({\mathrm{Cl}}_2\right)$ react to form a single product Hydrogen chloride $\left(\mathrm{HCl}\right)$. Therefore, it is categorized as a combination reaction.

Explanation for incorrect options:

(A)

• The reaction in which a single reactant breaks down into two or more products is termed a decomposition reaction. Example:

$\underset{\mathrm{Calcium}\mathrm{Carbonate}\mathrm{or}\mathrm{Limestone}}{{\mathrm{CaCO}}_3\left(\mathrm{s}\right)}\stackrel{∆}{\to }\underset{\mathrm{Calcium}\mathrm{oxide}\mathrm{or}\mathrm{quicklime}}{\mathrm{CaO}\left(\mathrm{s}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2}$

(B)

• In a single displacement reaction, a more reactive element displaces a less reactive element from its compound form two product molecules. Example:

$\underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\mathrm{Copper}\left(\mathrm{II}\right)\mathrm{sulfate}}{{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)}\to \underset{\mathrm{Zinc}\mathrm{sulfate}}{{\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)}+\underset{\mathrm{Copper}}{\mathrm{Cu}\left(\mathrm{s}\right)}$

(D)

• In an isomerization reaction, one isomer of any molecule is converted into another isomer. Example:

$\underset{\mathrm{Butane}\mathrm{or}\mathrm{n}-\mathrm{butane}}{{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_3\left(\mathrm{g}\right)}\leftrightarrow \underset{2-\mathrm{methylpropane}\mathrm{or}\mathrm{Isobutane}}{{\mathrm{CH}}_3\mathrm{CH}\left({\mathrm{CH}}_3\right){\mathrm{CH}}_3\left(\mathrm{g}\right)}$

• Since, ${\mathrm{H}}_2$, ${\mathrm{Cl}}_2$, and $\mathrm{HCl}$ are not isomers of each other, the given reaction is not an isomerization reaction.

Hence, option C is correct. The reaction, ${\mathrm{H}}_2+{\mathrm{Cl}}_2\to 2\mathrm{HCl}$ is a combination reaction.