Problem 20 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Match the following : Column I \(\quad\) Column II (A) \(\mathrm{Bi}^{3+} \rightarrow(\mathrm{BiO})^{+}\) (p) Heat (B) \(\left[\mathrm{AlO}_{2}\right]^{-} \rightarrow \mathrm{Al}(\mathrm{OH})_{3}\) (q) Hydrolysis (C) \(\left[\mathrm{SiO}_{4}\right]^{4-} \rightarrow\left[\mathrm{Si}_{2} \mathrm{O}_{7}\right]^{6-}\) (r) Acidification (D) \(\left[\mathrm{B}_{4} \mathrm{O}_{7}\right]^{2-} \rightarrow\left[\mathrm{B}(\mathrm{OH})_{3}\right]\) (s) Dilution by water

Step-by-Step Solution

Answer

(A) p, (B) q, (C) r, (D) s.

Step 1: Analyzing Reaction (A)

The transformation \(\mathrm{Bi}^{3+} \rightarrow (\mathrm{BiO})^{+}\) involves the oxidation of bismuth ion to bismuth oxide ion. This typically occurs due to the application of heat, leading to the removal of oxygen from BiO. Thus, this reaction is matched with heat (p).

Step 2: Analyzing Reaction (B)

The transformation \(\left[\mathrm{AlO}_{2}\right]^{-} \rightarrow \mathrm{Al}(\mathrm{OH})_{3}\) involves converting an aluminate ion into aluminum hydroxide. This is a typical hydrolysis reaction involving the addition of water to form a hydroxide, so it matches with hydrolysis (q).

Step 3: Analyzing Reaction (C)

The transformation \(\left[\mathrm{SiO}_{4}\right]^{4-} \rightarrow \left[\mathrm{Si}_{2}\mathrm{O}_{7}\right]^{6-}\) involves the condensation of silicate units to form a disilicate. Such transformations usually take place in acidic conditions to facilitate polymerization, hence it matches with acidification (r).

Step 4: Analyzing Reaction (D)

The transformation \(\left[\mathrm{B}_{4}\mathrm{O}_{7}\right]^{2-} \rightarrow \left[\mathrm{B}(\mathrm{OH})_{3}\right]\) describes the conversion of borate into boric acid. This conversion requires water, and generally occurs during dilution, thus dilution by water (s) is appropriate.

Key Concepts

Oxidation Reactions

Oxidation reactions are chemical processes that involve the loss of electrons or an increase in oxidation state. In a simple sense, they often involve the addition of oxygen or the removal of hydrogen from a substance. A well-known example is when metals like iron rust when exposed to moist air. Here, iron loses electrons to oxygen, forming iron oxide.

In the context of the equation given in the exercise, the reaction \(\mathrm{Bi}^{3+} \rightarrow (\mathrm{BiO})^{+}\) represents an oxidation reaction. The bismuth ion (\(\mathrm{Bi}^{3+}\)) is oxidized to form a bismuth oxide ion ((\mathrm{BiO})^{+}), typically through the application of heat. This process implies removal of oxygen atoms under high temperatures.

• Occurs with element losing electrons
• Often results in the formation of oxides
• Can involve energy changes like heat

Oxidation is a crucial concept in inorganic reactions as it helps understand reactions involving metals, nonmetals, and various compounds in everyday life.

Hydrolysis

Hydrolysis is a reaction involving the breaking of a bond in a molecule using water. A typical hydrolysis reaction occurs when a compound reacts with water and breaks down into two or more separate products. This process is vital in biology for the breakdown of complex molecules like proteins and carbohydrates.

In the initial exercise, the reaction \([\mathrm{AlO}_{2}]^{-} \rightarrow \mathrm{Al}(\mathrm{OH})_{3}\) is an example of hydrolysis. Here, the aluminate ion reacts with water to form aluminum hydroxide. Water splits during the reaction to add hydrogen (\(\mathrm{H}^{+}\)) and hydroxide (\(\mathrm{OH}^{-}\)) ions, converting the compounds into simpler forms.

• Involves addition of water
• Breaks complex molecules into simpler forms
• Directly impacts solutions by adding ions

Understanding hydrolysis helps in comprehending how many industrial and biological processing reactions occur, such as digestion in living organisms.

Condensation Reactions

Condensation reactions are chemical reactions where two or more molecules combine to form a larger molecule, usually accompanied by the loss of a small molecule such as water. This type of reaction is prevalent in organic chemistry but is also significant in inorganic reactions.

In the exercise, the transformation \([\mathrm{SiO}_{4}]^{4-} \rightarrow [\mathrm{Si}_{2}\mathrm{O}_{7}]^{6-}\) involves a condensation reaction. Here, silicate ions join to form a disilicate compound, leading to the loss of water. Acidic conditions usually facilitate such transformations, acting as a catalyst to promote these reactions.

• Combines smaller molecules into larger compounds
• Often liberates a molecule like water or alcohol
• Essential for forming complex structures like polymers

Condensation reactions are fundamental to understanding the synthesis of various materials and biological macromolecules.

Polymerization

Polymerization is the process where small molecular units called monomers join together to form a large chain or network molecule, known as a polymer. These reactions are crucial in creating various materials, from plastics to DNA.

Typically, polymerization can occur through addition (where monomers add to a growing chain) or condensation (involving the loss of small molecules like water). The equation given in reaction C \([\mathrm{SiO}_{4}]^{4-} \rightarrow [\mathrm{Si}_{2}\mathrm{O}_{7}]^{6-}\) shows a step that is part of a condensation polymerization process, where single units join together to form more complex structures.

• Monomers form long or cross-linked polymers
• Two main types: Addition and Condensation
• Creates polymers used in diverse industrial applications

Polymerization is essential in everyday materials, from synthetic fabrics to natural biopolymers, making it a key concept in both chemistry and materials science.