Problem 83 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Match the following, choosing one item from column \(\mathbf{X}\) and one from column Y. (i) \(\mathrm{Hg}_{2} \mathrm{Cl}_{2}\) (ii) \(\left(\mathrm{NaPO}_{3}\right)_{n}\) (iii) \(\mathrm{NO}_{3}^{-}\) (iv) \(\mathrm{SnO}_{2}\) (v) \(\quad \mathrm{KCl} . \mathrm{MgCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\) (vi) \(\mathrm{AgNO}_{3}\) \(\mathbf{X} \quad \mathbf{Y}\) (a) cassiterite (b) lunar caustic (c) producer gas (d) water softener (e) brown ring test (f) carnallite (vii) \(\mathrm{CO}+\mathrm{N}_{2}\) (g) calomel

Step-by-Step Solution

Answer

(i) g, (ii) d, (iii) e, (iv) a, (v) f, (vi) b, (vii) c.

Step 1: Pairing Compound \( \mathrm{Hg}_{2} \mathrm{Cl}_{2} \)

The compound \( \mathrm{Hg}_{2} \mathrm{Cl}_{2} \) is known by its common name 'calomel'. Therefore, \( \mathrm{Hg}_{2} \mathrm{Cl}_{2} \) pairs with option (g) calomel.

Step 2: Pairing Compound \( \left(\mathrm{NaPO}_{3}\right)_{n} \)

\( \left(\mathrm{NaPO}_{3}\right)_{n} \) is a sodium polyphosphate, which is commonly used as a water softener. Therefore, \( \left(\mathrm{NaPO}_{3}\right)_{n} \) pairs with option (d) water softener.

Step 3: Pairing Ion \( \mathrm{NO}_{3}^{-} \)

The nitrate ion \( \mathrm{NO}_{3}^{-} \) is involved in the formation of a brown ring in the 'brown ring test' for nitrates. Therefore, \( \mathrm{NO}_{3}^{-} \) pairs with option (e) brown ring test.

Step 4: Pairing Compound \( \mathrm{SnO}_{2} \)

\( \mathrm{SnO}_{2} \) is known as cassiterite, a mineral form of tin dioxide. Therefore, \( \mathrm{SnO}_{2} \) pairs with option (a) cassiterite.

Step 5: Pairing Compound \( \mathrm{KCl} . \mathrm{MgCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O} \)

\( \mathrm{KCl} . \mathrm{MgCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O} \) is known as carnallite. Therefore, \( \mathrm{KCl} . \mathrm{MgCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O} \) pairs with option (f) carnallite.

Step 6: Pairing Compound \( \mathrm{AgNO}_{3} \)

\( \mathrm{AgNO}_{3} \) is commonly referred to as lunar caustic. Therefore, \( \mathrm{AgNO}_{3} \) pairs with option (b) lunar caustic.

Step 7: Pairing Compound \( \mathrm{CO} + \mathrm{N}_{2} \)

The combination of carbon monoxide and nitrogen \( \mathrm{CO} + \mathrm{N}_{2} \) forms what is known as producer gas. Therefore, \( \mathrm{CO} + \mathrm{N}_{2} \) pairs with option (c) producer gas.

Key Concepts

Chemical Compounds

Chemical compounds are substances formed by the chemical combination of two or more different elements, held together by chemical bonds. These compounds can be classified based on the types of bonds that hold the atoms together:

• Covalent bonds: where electrons are shared between atoms
• Ionic bonds: where electrons are transferred from one atom to another
• Metallic bonds: where electrons move freely between a lattice of metal atoms

Each compound exhibits properties different from the elements that compose it. For example, when individual elements like mercury (\( ext{Hg} \)) and chlorine (\( ext{Cl} \)) combine to form mercury(I) chloride (\( \text{Hg}_{2}\text{Cl}_{2} \)), they create a compound with distinct properties known as calomel. Understanding the properties and interactions of chemical compounds is critical for predicting how they behave in various situations.

Common Names

In chemistry, many compounds are known by their common names as well as their chemical names. Common names often derive from historical or traditional contexts and might not reflect the chemical composition. These names are helpful in everyday discourse but can be confusing due to their lack of systematic naming.

• Calomel: The compound \( \text{Hg}_{2}\text{Cl}_{2} \), known scientifically as mercury(I) chloride, is called calomel. This name is derived from ancient alchemical practices.
• Lunar Caustic: Silver nitrate (\( \text{AgNO}_{3} \)), called lunar caustic, originates from the time when silver was associated with the moon (luna) in alchemy.
• Carnallite: \( \text{KCl} \cdot \text{MgCl}_2 \cdot 6\text{H}_2\text{O} \) is known as carnallite and is named after the mineral from which it was first isolated.

Common names remain prevalent, particularly in industrial and commercial sectors, despite the presence of systematic IUPAC naming conventions.

Chemical Reactions

Chemical reactions are processes where reactants transform into products, involving the breaking and forming of chemical bonds. These reactions are essential in understanding how substances interact and change. They can be categorized into several types based on their characteristics:

• Synthesis reactions: where simpler substances combine to form a more complex compound.
• Decomposition reactions: where a compound breaks down into simpler substances.
• Single and double displacement reactions: where elements or groups in reactants swap places.
• Combustion reactions: where substances react rapidly with oxygen, often producing heat and light.

Producer gas is an example of a product from a synthesis reaction where carbon monoxide (\( \text{CO} \)) and nitrogen (\( \text{N}_{2} \)) are formed by the partial combustion of hydrocarbon fuels. Understanding these reactions helps chemists design processes for everything from industrial production to energy generation.

Chemical Tests

Chemical tests are conducted to identify the presence or concentration of a chemical compound or element in a sample. These tests rely on the unique properties of substances and can involve physical or chemical changes that are often visually apparent.

• Brown Ring Test: Specifically designed to detect nitrate ions (\( \text{NO}_{3}^{-} \)), this test involves adding iron(II) sulfate (\( \text{FeSO}_{4} \)) to a solution containing nitrates and carefully layering concentrated sulfuric acid (\( \text{H}_2\text{SO}_4 \)) below it. The formation of a brown ring at the interface indicates the presence of nitrates.
• Flame Tests: Useful for identifying certain metal ions based on the characteristic color they emit when heated in a flame.
• Titrations: To determine the concentration of an unknown substance by reacting it with a standard solution.

These tests are crucial in laboratories for confirming chemical identities, testing purity, and developing new materials. It's fascinating how simple visual indicators can reveal complex chemical compositions.