Problem 182 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following Column-I (a) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) (b) \(\mathrm{HPO}_{3}\) (c) \(\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7}\) (d) \(\mathrm{H}_{3} \mathrm{PO}_{2}\) Column-II (p) Can react with \(\mathrm{AgNO}_{3}\) (q) In water softener (r) \(\mathrm{sp}^{3}\) hybridisation (s) Monobasic

Step-by-Step Solution

Answer

(a) matches with (r), (b) with (p), (c) with (q), and (d) with (s).

Step 1: Identify each compound in Column-I

Examine the molecular formulas in Column-I and determine the type of acid they represent. (a) \( \mathrm{H}_{3} \mathrm{PO}_{4} \) is phosphoric acid.(b) \( \mathrm{HPO}_{3} \) is metaphosphoric acid.(c) \( \mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7} \) is pyrophosphoric acid.(d) \( \mathrm{H}_{3} \mathrm{PO}_{2} \) is hypophosphorous acid.

Step 2: Match acids with properties in Column-II

Go through each property in Column-II and match it with the corresponding compound in Column-I based on the chemical properties and composition of the acids.(p) Can react with \( \mathrm{AgNO}_{3} \): \( \mathrm{HPO}_{3} \) (b) - Metaphosphoric acid (can react with silver nitrate forming a silver phosphate precipitate).(q) In water softener: \( \mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7} \) (c) - Pyrophosphoric acid (used in the preparation of phosphate detergents, which act as water softeners).(r) \( \mathrm{sp}^{3} \) hybridisation: \( \mathrm{H}_{3} \mathrm{PO}_{4} \) (a) - Phosphoric acid (the phosphorus atom in \( \mathrm{H}_{3} \mathrm{PO}_{4} \) has \( \mathrm{sp}^{3} \) hybridisation).(s) Monobasic: \( \mathrm{H}_{3} \mathrm{PO}_{2} \) (d) - Hypophosphorous acid (has one ionizable hydrogen atom and hence is monobasic).

Step 3: Write down the final matches

Summarize the pairs identified in the previous step to produce the final matching result.(a) \( \mathrm{H}_{3} \mathrm{PO}_{4} \) matches with (r) \( \mathrm{sp}^{3} \) hybridisation.(b) \( \mathrm{HPO}_{3} \) matches with (p) Can react with \( \mathrm{AgNO}_{3} \).(c) \( \mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7} \) matches with (q) In water softener.(d) \( \mathrm{H}_{3} \mathrm{PO}_{2} \) matches with (s) Monobasic.

Key Concepts

Acids and Bases

Acids and bases are fundamental concepts in inorganic chemistry, playing vital roles in various chemical processes. An acid is a compound that can donate a proton ( +1 ion) in a reaction, making it a proton donor. Bases, on the other hand, accept protons, acting as proton acceptors. Understanding these definitions helps in deciphering how different substances will interact in solutions.

Acids can be categorized based on their ionizable hydrogen atoms. For instance:

• Monobasic acids have a single ionizable hydrogen atom, like hypophosphorous acid ( H_3PO_2 ), and are involved in single-step ionization processes.
• Dibasic acids contain two hydrogen ions that can be released, leading to a two-step ionization process.
• Tribasic acids, such as phosphoric acid ( H_3PO_4 ), can release three ions.

This categorization influences how acids react chemically and how they are used in various applications, such as in buffering systems or in the creation of salts.

Molecular Formulas

Molecular formulas specify the number and type of atoms in a molecule, offering insight into the molecular structure and properties. For example, ( H_3PO_4 ) indicates three hydrogen, one phosphorus, and four oxygen atoms, representing phosphoric acid. This formula tells us not only what atoms are present but also hints at the potential chemical properties and reactivity of the compound.

Understanding these formulas is crucial for identifying compounds' roles in chemical reactions or processes:

• Structural properties can be extrapolated from molecular formulas, aiding in determining physical properties like solubility and boiling points.
• Molecular formulas help chemists predict reactivity by showing how atoms might interact in chemical reactions.

Thus, deciphering molecular formulas enables chemists to understand the roles these substances play in more significant chemical frameworks.

Chemical Properties

Chemical properties define how a substance reacts with others, playing a crucial role in determining the practical applications of a compound. Understanding these properties can guide predictions regarding the behaviors of different chemical species under specific conditions.

For instance:

• Metaphosphoric acid ( HPO_3 ) can react with ( AgNO_3 ) to form silver phosphate, a precipitation reaction showcasing reactivity.
• Pyrophosphoric acid ( H_4P_2O_7 ) is used in water softeners, reflecting its ability to bind ions like calcium, which may impair water usage.

Through the lens of chemical properties, we can better understand why certain reactions occur and how these substances can be effectively utilized in industrial or laboratory settings.

Hybridisation

Hybridisation is a concept in chemistry where atomic orbitals mix to form new hybrid orbitals. This affects both the geometry and bonding character of molecules. Hybridisation helps explain molecule shapes and how atoms within a molecule interact chemically.

In the case of phosphoric acid ( H_3PO_4 ), phosphorus exhibits ( sp^3 ) hybridisation:

• The mixture of one s and three p orbitals results in four equivalent hybrid orbitals.
• This hybridisation leads to tetrahedral geometry, contributing to phosphoric acid’s stability and reactivity.

Understanding hybridisation is essential for predicting molecular shapes, which influences how molecules interact with one another in chemical reactions.

Water Softening

Water softening is a chemical process that removes hardness-causing minerals like calcium and magnesium from water. This process is crucial in improving water's quality and usability.

Pyrophosphoric acid ( H_4P_2O_7 ) plays a significant role in water softening due to its ability to act as a sequestering agent:

• It binds and inactivates calcium and magnesium ions, preventing scale buildup in pipelines or appliances.
• This chemical interaction prevents unwanted reactions that would otherwise result in mineral deposits.

By understanding the role of compounds like ( H_4P_2O_7 ) in water softening, one can appreciate the broader applications of inorganic chemistry in everyday life, particularly in maintaining equipment efficiency and improving water quality.