Hydrocarbons

Step 1: Understanding Stability of Diazonium Salts
- Diazonium salts have the general formula ,
where:
- represents an aromatic group.
- represents the anion, such as , etc.
- Most diazonium salts are water-soluble and unstable at room temperature, decomposing rapidly to release nitrogen gas.
Step 2: Properties of
- Benzenediazonium tetrafluoroborate is an exception.
- The tetrafluoroborate ion stabilizes the diazonium cation, making it:
- Insoluble in water (hence it precipitates).
- Stable at room temperature without decomposing.
Step 3: Conclusion
Among diazonium salts, benzenediazonium tetrafluoroborate is the most stable and water-insoluble at room temperature.

Step 1: Understanding Basic Strength of Amines
- The basic strength of amines depends on their ability to donate a lone pair of electrons on nitrogen.
- Alkyl groups increase electron density on nitrogen through the +I (inductive) effect, enhancing basicity.
- Aromatic amines have a resonance effect (-R effect), which delocalizes the lone pair of nitrogen into the benzene ring, reducing basicity.
Step 2: Comparing the Given Amines
1. Diethylamine has two ethyl groups, which exert a strong +I effect, making it the most basic.
2. Ethylamine has only one ethyl group, so it is slightly less basic than diethylamine.
3. Ammonia has no alkyl group, making it less basic than both ethylamine and diethylamine.
4. Aniline has a benzene ring, which withdraws electron density from nitrogen due to resonance (-R effect), making it the least basic.
Step 3: Conclusion
The correct order of basicity is:

Step 1: Understanding pKa and Acidity
- The pKa value is the negative logarithm of the acid dissociation constant ( ), which measures the strength of an acid.
- A lower pKa value indicates a stronger acid, meaning the acid ionizes more easily in solution.
Step 2: Comparing Carboxylic Acids
- Carboxylic acids ( ) have different pKa values depending on the electron-withdrawing or electron-donating nature of the substituent group ( ).
- Formic acid (HCOOH) has the lowest pKa value among carboxylic acids because:
- It lacks an alkyl group, so there is no electron-donating effect to stabilize the carboxylate ion.
- It is the simplest carboxylic acid, making it the strongest among its homologs.
Step 3: Conclusion
- Since HCOOH (Formic Acid) has the least pKa value, it is the strongest carboxylic acid among common carboxylic acids.

Step 1: Understanding Schiff's Base Formation
- A Schiff’s base is formed by the reaction between a carbonyl compound (aldehyde or ketone) and a primary amine.
- The reaction involves the nucleophilic attack of the amine ( ) on the carbonyl carbon of the ketone or aldehyde, forming an imine (-C=NR).
Step 2: Identifying 'R'
- The given reaction shows a ketone (CHsubscript{3}-CO-CHsubscript{3}, acetone) reacting to form a Schiff’s base.
- The nucleophile that reacts with acetone must be a primary amine.
- The primary amine that leads to the formation of a Schiff's base in this case is methylamine ( ).
Step 3: Conclusion
- The value of 'R' in this reaction is methylamine ( ), which reacts with acetone to form the Schiff's base.

Step 1: Identify the Oxidation State of Chromium
- The given complex is K[Cr(H₂O)₂(C₂O₄)₂].
- Potassium (K⁺) has a charge of +1.
- The ligands are:

H₂O (Water): Neutral ligand (charge = 0).

C₂O₄^2- (Oxalate): Bidentate ligand (charge = -2 each).

Step 2: Oxidation State Calculation
So, the oxidation state of Chromium (Cr) is +3.
Step 3: Coordination Number of Chromium
- H₂O (Water) is a monodentate ligand (2 × 1 = 2).
- C₂O₄^2- (Oxalate) is a bidentate ligand (2 × 2 = 4).
- Total coordination number: So, the coordination number of Chromium is 6.
Step 4: Conclusion
- The central metal ion is Cr³⁺.
- The coordination number is 6.

Step 1: Understanding the Lanthanide Series
The lanthanides (or rare earth elements) consist of 15 elements from lanthanum (La) to lutetium (Lu) in the periodic table.
Step 2: Oxidation States of Lanthanides
- The common oxidation state of lanthanides is .
- However, some lanthanides can exhibit other oxidation states, such as:
- (e.g., Eu, Yb, Sm)
- (e.g., Ce, Tb)
Step 3: Why Cerium Exhibits Oxidation State
- Electronic configuration of cerium: - In the oxidation state, cerium loses all its valence electrons: - This stable xenon-like configuration makes Ce stable.
Step 4: Conclusion
Among lanthanides, cerium (Ce) is the most common element to exhibit a oxidation state.

Step 1: Understanding the Oxidizing Action of KMnO₄ in Acidic Medium
- Potassium permanganate (KMnO₄) is a strong oxidizing agent.
- In acidic medium, it undergoes reduction, converting Mn in ⁺⁷ oxidation state to Mn in ⁺² oxidation state.
Step 2: Balanced Redox Reaction in Acidic Medium
The half-reaction for the reduction of permanganate ion in acidic solution is: This means that one mole of MnO₄^- accepts 5 electrons to form Mn²⁺.
Step 3: Ratio of Electrons Gained to MnO₄^- Ions Reduced
- The equivalent weight concept states that the oxidizing action in acidic medium follows a 2:5 ratio.
- This means that for every 2 moles of MnO₄^-, 5 moles of electrons are transferred.
Step 4: Conclusion
Thus, the oxidizing action of KMnO₄ in acidic solution follows the ratio .