CHEMISTRY

CHEMISTRY

A compound has an empirical formula CHâ‚‚ and a molar mass of 70 g/mol. What is its molecular formula? (Atomic masses: C

Given: A compound has an empirical formula CH₂ and a molar mass of 70 g/mol. What is its molecular formula? (Atomic masses: C = 12, H = 1) These values define the system as per NCERT data. Formula: Empirical mass = 12 + (2 × 1) = 14 g/mol. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: n = 70 / 14 = 5. Molecular formula = C₅H₁₀. Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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CHEMISTRY

What is the geometry of the nitrogen atom in CH₃NH₃+ ?

In CH₃NH₃+, the conjugate acid of methylamine, nitrogen has four bonds (three to H, one to C) and no lone pair, resulting in a tetrahedral geometry.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Relevant Chemistry topic covering principles and examples as per NCERT.

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CHEMISTRY

What is the product when CH₃CH₂NH₂ reacts with CH₃CH₂COCH₃ followed by H₂/Ni ?

Ethanamine reacts with butan-2-one ( CH₃CH₂COCH₃ ) to form an imine, reduced by H₂/Ni to CH₃CH₂NHCH(CH₃)CH₂CH₃ (N-(butan-2-yl)ethanamine). This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Relevant Chemistry topic covering principles and examples as per NCERT.

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CHEMISTRY

Which of the following reactions confirms the presence of a primary aromatic amine?

Bromination with Br₂ in water forms 2, 4, 6-tribromoaniline from aniline ( C₆H₅NH₂ ), a specific test for primary aromatic amines due to the activating -NH₂ group.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Relevant Chemistry topic covering principles and examples as per NCERT.

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CHEMISTRY

Which of the following compounds does not undergo nucleophilic addition reactions?

Carboxylic acids do not undergo nucleophilic addition reactions because the carbonyl carbon is less electrophilic due to resonance stabilization. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Relevant Chemistry topic covering principles and examples as per NCERT.

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CHEMISTRY

What is the correct IUPAC name of glycerol?

Glycerol is a trihydroxy compound and its IUPAC name is propane-1, 2, 3-triol. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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CHEMISTRY

Which compound is used as an industrial solvent and paint remover?

Dichloromethane (DCM) is widely used for these purposes. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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CHEMISTRY

The product formed when KMnOâ‚„ oxidizes NOâ‚‚^- in acidic medium is:

5NO₂^- + 2MnO₄^- + 6H^+ -> 2Mn^{2+ + 5NO₃^- + 3H₂O . Nitrite ( NO₂^- ) is oxidized to nitrate ( NO₃^- ). This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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CHEMISTRY

Calculate the freezing point depression of a solution made by dissolving 6 g of urea ( NHâ‚‚CONHâ‚‚ ) in 200 g of water.

Given: Calculate the freezing point depression of a solution made by dissolving 6 g of urea ( NH₂CONH₂ ) in 200 g of water. ( K_f = 1.86 K kg/mol, Molar mass of urea = 60 g/mol ) These values define the system as per NCERT data. Formula: Moles of urea = 6/60 = 0.1 mol. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Molality = 0.1/0.2 = 0.5 mol/kg . Δ T_f = 1.86 × 0.5 = 0.93 K . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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CHEMISTRY

What happens when propyne is treated with ammoniacal silver nitrate solution?

Terminal alkynes react with ammoniacal silver nitrate to form a white precipitate of silver acetylide. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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CHEMISTRY

Which of the following elements is a chalcogen?

Chalcogens are Group 16 elements. Oxygen (O) belongs to this group, unlike F (Group 17), Na (Group 1), or Si (Group 14). This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Relevant Chemistry topic covering principles and examples as per NCERT.

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CHEMISTRY

Which compound reacts with Fehling’s solution to give a red precipitate?

Aldehydes reduce Fehling’s solution to give a red precipitate of Cu₂O, while ketones do not. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.

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