Question

On heating, Ammonia $\left({\mathrm{NH}}_3\right)$ gives Nitrogen $\left({\mathrm{N}}_2\right)$ and Hydrogen $\left({\mathrm{H}}_2\right)$.Hydrogen on treatment with Chlorine $\left({\mathrm{Cl}}_2\right)$gas forms Hydrogen chloride gas $\left(\mathrm{HCl}\right)$.Hydrogen chloride on dissociation in water $\left({\mathrm{H}}_2\mathrm{O}\right)$ forms Hydrochloric acid. Hydrochloric acid on treatment with Sodium hydroxide $\left(\mathrm{NaOH}\right)$ forms Sodium chloride $\left(\mathrm{NaCl}\right)$ and water. Sodium chloride thus formed on treatment with Silver nitrate $\left({\mathrm{AgNO}}_3\right)$ forms Silver chloride $\left(\mathrm{AgCl}\right)$ and Sodium nitrate $\left({\mathrm{NaNO}}_3\right)$.

various types of reaction involved in the above process are given below:

(A) Combination reaction

(B) Neutralization reaction

(C) Precipitation reaction

(D) Decomposition reaction

Arrange them in a proper sequence as given above.

• A. ADCB
• B. ADBC
• C. DACB
• D. DABC

Answer 1

The correct option is D

DABC

Explanation:

Step 1: On heating, Ammonia $\left({\mathrm{NH}}_3\right)$ gives Nitrogen $\left({\mathrm{N}}_2\right)$ and Hydrogen $\left({\mathrm{H}}_2\right)$

$\underset{\left(\mathrm{Ammonia}\right)}{2{\mathrm{NH}}_3\left(\mathrm{g}\right)}\stackrel{∆}{\to }\underset{\left(\mathrm{Nitrogen}\right)}{{\mathrm{N}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Hydrogen}\right)}{3{\mathrm{H}}_2\left(\mathrm{g}\right)}$

• Whenever a single reactant breaks down into two or more product then it is known as Decomposition reaction.
• Hence above reaction is decomposition reaction.

Step 2:.Hydrogen on treatment with Chlorine gas $\left({\mathrm{Cl}}_2\right)$ forms Hydrogen chloride gas $\left(\mathrm{HCl}\right)$.

$\underset{\left(\mathrm{Hydrogen}\right)}{{\mathrm{H}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Chlorine}\right)}{{\mathrm{Cl}}_2\left(\mathrm{g}\right)}\to \underset{\left(\mathrm{Hydrogen}\mathrm{chloride}\right)}{2\mathrm{HCl}\left(\mathrm{g}\right)}$

• Whenever two or more reactant combine two form a single product then it is known as Combination reaction.
• Hence above reaction is Combination reaction.

Step 3: Hydrogen chloride on dissociation in water $\left({\mathrm{H}}_2\mathrm{O}\right)$ forms Hydrochloric acid.

$\underset{(\mathrm{Hydrogen}\mathrm{chloride})}{\mathrm{HCl}\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Water}\right)}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\rightleftharpoons \underset{\left(\mathrm{Hydronium}\mathrm{ion}\right)}{{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)}+\underset{\left(\mathrm{Chloride}\mathrm{ion}\right)}{{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)}$

• The solution that result is called Hydrochloric acid. and reaction is known as Ionic reaction.

Step 4: Hydrochloric acid on treatment with Sodium hydroxide $\left(\mathrm{NaOH}\right)$ forms Sodium chloride $\left(\mathrm{NaCl}\right)$ and water.

$\underset{\left(\mathrm{Hydrochloric}\mathrm{acid}\right)}{\mathrm{HCl}\left(\mathrm{aq}\right)}+\underset{\left(\mathrm{Sodium}\mathrm{hydroxide}\right)}{\mathrm{NaOH}\left(\mathrm{s}\right)}\to \underset{\left(\mathrm{Sodium}\mathrm{chloride}\right)}{\mathrm{NaCl}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Water}\right)}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$.

• Acid and base reacts to form salt and water this reaction is known as Neutralization reaction.
• In above reaction Hydrochloric acid reacting with Sodium hydroxide base to form Sodium chloride salt and water. Hence it is a neutralization reaction.

Step 5: Sodium chloride on treatment with Silver nitrate $\left({\mathrm{AgNO}}_3\right)$ forms Silver chloride $\left(\mathrm{AgCl}\right)$ and Silver nitrate $\left({\mathrm{NaNO}}_3\right)$

$\underset{\left(\mathrm{Silver}\mathrm{nitrate}\right)}{{\mathrm{AgNO}}_3\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Sodium}\mathrm{chloride}\right)}{\mathrm{NaCl}\left(aq\right)}\to \underset{\left(\mathrm{Silver}\mathrm{chloride}\right)}{\mathrm{AgCl}\left(aq\right)}+\underset{\left(\mathrm{Sodium}\mathrm{nitrate}\right)}{{\mathrm{NaNO}}_3\left(\mathrm{s}\right)}$

• A Chemical reaction in which formation of insoluble salt occur then it is known as Precipitation reaction and insoluble salt is known as Precipitate.
• In above reaction insoluble salt Silver chloride is formed which is a Precipitate hence above reaction is Precipitation reaction.

So the correct order of reaction is Decomposition reaction, Combination reaction, Neutralization reaction and Precipitation reaction i.e. DABC.

Hence the correct answer is (D).