Problem 18 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

. Write balanced equations for the reactions of the following compounds with water : [2002-5 Marks] (i) \(\mathrm{Al}_{4} \mathrm{C}_{3}\) (ii) \(\mathrm{CaNCN}\) (iii) \(\mathrm{BF}_{3}\) (iv) \(\mathrm{NCl}_{3}\) (v) \(\mathrm{XeF}_{4}\)

Step-by-Step Solution

Answer

(i) \(\mathrm{Al}_4\mathrm{C}_3 + 12\mathrm{H}_2\mathrm{O} \rightarrow 3\mathrm{CH}_4 + 4\mathrm{Al(OH)}_3\); (ii) \(\mathrm{CaNCN} + 3\mathrm{H}_2\mathrm{O} \rightarrow \mathrm{CaCO}_3 + \mathrm{NH}_3\); (iii) \(\mathrm{BF}_3 + 3\mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}_3\mathrm{BO}_3 + 3\mathrm{HF}\); (iv) \(\mathrm{NCl}_3 + 3\mathrm{H}_2\mathrm{O} \rightarrow \mathrm{NH}_3 + 3\mathrm{HOCl}\); (v) \(6\mathrm{XeF}_4 + 12\mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{Xe} + 4\mathrm{XeF}_2 + 24\mathrm{HF} + 3\mathrm{O}_2\).

Step 1: Reaction of Aluminum Carbide

When aluminum carbide (\( \mathrm{Al}_4\mathrm{C}_3 \)) reacts with water, it produces methane and aluminum hydroxide. The balanced chemical equation for this reaction is:\[ \mathrm{Al}_4\mathrm{C}_3 + 12\ \mathrm{H}_2\mathrm{O} \rightarrow 3\ \mathrm{CH}_4 + 4\ \mathrm{Al(OH)}_3 \]

Step 2: Reaction of Calcium Cyanamide

Calcium cyanamide (\( \mathrm{CaNCN} \)) reacts with water to form calcium carbonate and ammonia. The balanced equation is:\[ \mathrm{CaNCN} + 3\ \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{CaCO}_3 + \mathrm{NH}_3 \]

Step 3: Reaction of Boron Trifluoride

When boron trifluoride (\( \mathrm{BF}_3 \)) reacts with water, it undergoes hydrolysis to form boric acid and hydrofluoric acid. The balanced equation is:\[ \mathrm{BF}_3 + 3\ \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}_3\mathrm{BO}_3 + 3\ \mathrm{HF} \]

Step 4: Reaction of Nitrogen Trichloride

Nitrogen trichloride (\( \mathrm{NCl}_3 \)) reacts with water to produce ammonia and hypochlorous acid. The balanced equation is:\[ \mathrm{NCl}_3 + 3\ \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{NH}_3 + 3\ \mathrm{HOCl} \]

Step 5: Reaction of Xenon Tetrafluoride

Xenon tetrafluoride (\( \mathrm{XeF}_4 \)) reacts with water to form xenon, xenon difluoride, oxygen difluoride, and hydrofluoric acid. The balanced equation is:\[ 6\ \mathrm{XeF}_4 + 12\ \mathrm{H}_2\mathrm{O} \rightarrow 2\ \mathrm{Xe} + 4\ \mathrm{XeF}_2 + 24\ \mathrm{HF} + 3\ \mathrm{O}_2 \]

Key Concepts

Chemical Reactions

A chemical reaction involves a transformation where substances, known as reactants, change into new substances called products. These transformations are represented by chemical equations, which must be balanced to comply with the law of conservation of mass. This means, for every atom of an element on the reactant side, the same number must appear on the product side.
This ensures that no atoms are lost or gained during the reaction. In the reactions given in the exercise, each compound reacts with water to produce new compounds:

• Aluminum carbide and water yield methane and aluminum hydroxide.
• Calcium cyanamide and water form calcium carbonate and ammonia.
• Boron trifluoride and water produce boric acid and hydrofluoric acid.
• Nitrogen trichloride and water create ammonia and hypochlorous acid.
• Xenon tetrafluoride and water result in xenon, xenon difluoride, oxygen difluoride, and hydrofluoric acid.

Understanding the reactants and products is crucial to mastering chemical reactions.

Hydrolysis

Hydrolysis is a specific type of chemical reaction where a compound reacts with water, leading to the breakdown of that compound. This process often results in the formation of new substances. The term 'hydrolysis' derives from Greek, meaning 'water' and 'to unbind,' and it aptly describes the unbinding or breaking down through water's action. A common feature in many of the example reactions is hydrolysis, playing a significant role in transforming the reactants into their respective products.
For instance, in boron trifluoride, water molecules interact to produce boric acid and hydrofluoric acid, a classic hydrolysis process. Similarly, nitrogen trichloride undergoes hydrolysis when it reacts with water, forming ammonia and hypochlorous acid. Hydrolysis is essential for understanding how many chemical transformations occur in both inorganic and organic chemistry.

Stoichiometry

Stoichiometry is the aspect of chemistry that deals with the quantitative relationships of the elements and compounds involved in a chemical reaction. It helps us understand how much of each reactant is needed to form a given amount of product, and its principles are crucial for balancing chemical equations. In all of the reactions discussed, stoichiometry ensures the correct proportions of reactants for the complete reaction to occur. For example:

• In the aluminum carbide reaction, 12 water molecules are required for every unit of aluminum carbide to produce methane and aluminum hydroxide fully.
• The reaction of xenon tetrafluoride with water necessitates precise stoichiometric details to balance a complex reaction involving multiple products like xenon, xenon difluoride, and oxygen difluoride.

These calculations ensure a balanced equation where the number of atoms on each side matches, upholding the law of conservation of mass.

Inorganic Chemistry

Inorganic chemistry focuses on compounds that are not based on carbon-hydrogen bonds, contrary to organic chemistry. It deals with a wide range of substances like metals, minerals, and organometallic compounds. The exercises presented involve numerous inorganic compounds reacting with water, showcasing the diversity within inorganic chemistry:

• Aluminum carbide is a carbide compound typically studied in inorganic chemistry.
• Calcium cyanamide, used in fertilizers, is another inorganic material undergoing transformation.
• The noble gas compound xenon tetrafluoride, unusual due to xenon's reluctance to form compounds, reacts interestingly in an inorganic chemistry context.

These reactions highlight the varied nature of inorganic compounds and the wide scope of processes and reactions they undergo, illustrating inorganic chemistry's fundamental and practical aspects.