Problem 133 - A Complete Resource Book in Chemistry for JEE Main

Question

$$ \begin{array}{ll} \text { Column-I } & \text { Column-II } \\ \hline \begin{array}{ll} \text { (a) } \mathrm{Sn}+\text { conc. } \mathrm{HNO}_{3} & \text { (p) NO } \\\ \text { (b) } \mathrm{Sn}+\mathrm{di} . \mathrm{HNO}_{3} & \text { (q) } \mathrm{NO}_{2} \\ \text { (c) } \mathrm{Ag}+\text { conc. } \mathrm{HNO}_{3} & \text { (r) } \mathrm{NH}_{4} \mathrm{NO}_{3} \\ \text { (d) } \mathrm{Ag}+\text { dil. } \mathrm{HNO}_{3} & \text { (s) } \mathrm{Sn}\left(\mathrm{NO}_{3}\right)_{2} \\ & \text { (t) } \mathrm{AgNO}_{3} \end{array} \\ \text { (b) } \end{array} $$

Step-by-Step Solution

Answer

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

Step 1: Analyze Reaction of Sn with Conc. HNO3

When tin (Sn) reacts with concentrated nitric acid (HNO3), it leads to the formation of tin nitrate and nitrogen dioxide gas. Thus, the reaction can be symbolized as Sn + conc. HNO3 -> Sn(NO3)2 + NO2. Hence, (a) matches with (q).

Step 2: Analyze Reaction of Sn with Dil. HNO3

Tin (Sn) reacts with dilute nitric acid (HNO3) to produce tin nitrate and ammonium nitrate. This reaction is typically represented as Sn + dil. HNO3 -> Sn(NO3)2 + NH4NO3. Therefore, (b) matches with (r).

Step 3: Analyze Reaction of Ag with Conc. HNO3

Silver (Ag) with concentrated nitric acid forms silver nitrate and nitrogen dioxide. The reaction is modeled as Ag + conc. HNO3 -> AgNO3 + NO2. Hence, (c) matches with (q).

Step 4: Analyze Reaction of Ag with Dil. HNO3

When silver (Ag) reacts with dilute nitric acid, silver nitrate and nitrogen monoxide are produced. The reaction is expressed as Ag + dil. HNO3 -> AgNO3 + NO. So, (d) matches with (p).

Step 5: Compile the Matches

Based on the steps above, the matches are: (a) → (q) (b) → (r) (c) → (q) (d) → (p)

Key Concepts

Redox Reactions

Redox reactions, short for reduction-oxidation reactions, are a type of chemical reaction where the oxidation state of molecules are changed. This occurs through the transfer of electrons between two substances.

• "Oxidation" refers to the loss of electrons from a substance, resulting in an increase in its oxidation state.
• "Reduction" refers to the gain of electrons by a substance, leading to a decrease in its oxidation state.

During these reactions, one substance undergoes oxidation while the other undergoes reduction, forming a redox couple. When studying the reactions of tin (Sn) and silver (Ag) with nitric acid (HNO3), the distinct behaviors can be attributed to their redox properties. In the exercise, nitric acid acts as an oxidizing agent and facilitates these redox transformations by donating and accepting electrons. Understanding these underlying electron transfers can greatly illuminate why particular products, such as nitrogen dioxide or nitrogen monoxide, are formed in these reactions.

Nitric Acid Reactions

Nitric acid (HNO3) is a strong acid and a potent oxidizing agent that plays a critical role in various chemical reactions. It can react with both metals and non-metals, leading to a variety of outcomes based on its concentration.

• Concentrated Nitric Acid: Usually leads to oxidation reactions that produce nitrogen oxides like \( ext{NO}_2\) or \( ext{NO}\), and salts such as nitrates.
• Dilute Nitric Acid: Tends to produce different nitrogen oxides and in some cases can produce water-soluble nitrates.

In the reactions given in the exercise, tin and silver react with both concentrated and dilute nitric acid:- Tin with concentrated HNO3 produces tin nitrate and nitrogen dioxide.- With dilute HNO3, it produces tin nitrate and ammonium nitrate.- Silver in concentrated HNO3 results in silver nitrate and nitrogen dioxide.- Conversely, with dilute HNO3, silver yields silver nitrate and nitrogen monoxide.

Metal Nitrate Formation

Metal nitrates are crucial compounds, often formed during reactions involving metals and nitric acid. When such reactions occur, the metal cation combines with the nitrate anion to form a nitrate salt.In this exercise:- **Tin (\( ext{Sn}\))** reacts to form tin nitrate, \( ext{Sn(NO}_3)_2\), in both concentrated and dilute nitric acid. - **Silver (\( ext{Ag}\))**, reacting with either concentrated or dilute nitric acid, consistently produces silver nitrate, \( ext{AgNO}_3\).These nitrate salts are often soluble in water, making them relevant in various industrial and laboratory applications. Understanding this formation is key as it reflects both the reactivity and solubility properties of the transition metals and their compounds in different environments.

Matching Questions Chemistry

Matching types of questions are common in chemistry exams and tests. They aim to assess one's understanding of reaction outcomes, mechanisms, and products by selecting the correct pairings from multiple options. To master these questions:

• Identify Reactants: Understand the role and nature of each reactant, focusing on their chemical properties such as oxidation states.
• Know the Products: Memorize frequent products formed in standard reactions, such as common salts or gases.
• Review Reaction Conditions: Consider factors like temperature and concentration, which significantly affect the reaction process and outcomes.

By dissecting the reactions of tin and silver with nitric acid as in the exercise, students can enhance their problem-solving skills by correctly matching each reaction with its products. This strengthens the comprehension of not just the chemical principles involved, but also develops an intuitive grasp for anticipating products in redox reactions.