CHEMISTRY

CHEMISTRY

What is the formal charge on the nitrogen atom in the NO₂^- ion in one of its resonance structures?

In one resonance structure of NO₂^-, N has 1 double bond (4 electrons), 1 single bond (2 electrons), and 1 lone pair (2 electrons). Formal charge = 5 - 2 - 1/2 × 6 = 0.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII), Chapter: Chemical Bonding (Latest NCERT 2026-27), Topic: Hybridization of nitrogen in CH₃NH₂, sp³ hybridization and pyramidal geometry

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CHEMISTRY

What is the formal charge on the oxygen atom in the CO molecule?

In CO, oxygen has 1 triple bond (6 electrons) and 1 lone pair (2 electrons). Formal charge = 6 - 2 - 1/2 × 6 = +1. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII), Chapter: Electrochemistry (Latest NCERT 2026-27), Topic: Faraday's laws, charge required to reduce Al³⁺, 3F = 3 × 96500 C

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CHEMISTRY

A solution contains 10 g of a non-volatile solute (molar mass 200 g/mol) in 190 g of water. What is the molality of the

Given: A solution contains 10 g of a non-volatile solute (molar mass 200 g/mol) in 190 g of water. What is the molality of the solution? Formula: Moles of solute = 10/200 = 0.05 mol. Substitution & Calculation: Mass of solvent in kg = 190/1000 = 0.19 kg . Molality = 0.05/0.19 = 0.263 mol/kg . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII)Topic: Mole concept, atomic structure, chemical formulas like H₂O, CO₂, CH₃CH₂NH₂ and periodic trends.

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CHEMISTRY

A first-order reaction has a half-life of 35 minutes. What fraction of the reactant remains after 70 minutes?

Given: A first-order reaction has a half-life of 35 minutes. What fraction of the reactant remains after 70 minutes? Formula: k = 0.693/35 = 0.0198 min^{-1. Substitution & Calculation: ln frac[R]_0[R] = 0.0198 × 70 = 1.386, frac[R][R]_0 = e^{-1.386 = 0.25 . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII)Topic: Mole concept, atomic structure, chemical formulas like H₂O, CO₂, CH₃CH₂NH₂ and periodic trends.

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CHEMISTRY

How much current (in amperes) is required to deposit 0.159 g of copper from CuSO₄ solution in 482.5 seconds? (Molar mass

Given: How much current (in amperes) is required to deposit 0.159 g of copper from CuSO₄ solution in 482.5 seconds? (Molar mass of Cu = 63.5 g/mol, F = 96500 C/mol) Formula: Moles of Cu = 0.159/63.5 = 0.0025 mol. Substitution & Calculation: Reaction: Cu²⁺ + 2e⁻ → Cu(s), 2F deposits 63.5 g. . Charge = 0.0025 × 2 × 96500 = 482.5 C . Current = Q/t = 482.5/482.5 = 1 A . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII), Chapter: Electrochemistry (Latest NCERT 2026-27), Topic: Faraday's laws, charge required to reduce Al³⁺, 3F = 3 × 96500 C

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CHEMISTRY

A first-order reaction has a rate constant of 0.0577 min^{-1 . What is the half-life in minutes?

Given: A first-order reaction has a rate constant of 0.0577 min^{-1 . What is the half-life in minutes? Formula: t_{1/2 = 0.693/k = 0.693/0.0577 = 12 min .. Substitution: Substituting given values into formula as per NCERT 2026-27 method. Calculation: Simplifying step by step with proper SI units like m/s², J kg⁻¹ K⁻¹, 10⁻⁵, A m⁻¹ etc. Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII), Chapter: Chemical Kinetics (Latest NCERT 2026-27), Topic: Arrhenius equation, k = A e^(-E_a/RT), activation energy and rate constant

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CHEMISTRY

How many electrons are present in an ion with 16 protons, 16 neutrons, and a charge of -2?

Given: How many electrons are present in an ion with 16 protons, 16 neutrons, and a charge of -2? Formula: For a neutral atom, electrons = protons = 16. Substitution & Calculation: A charge of -2 means 2 extra electrons, so total electrons = 16 + 2 = 18. Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII), Chapter: Electrochemistry (Latest NCERT 2026-27), Topic: Faraday's laws, charge required to reduce Al³⁺, 3F = 3 × 96500 C

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CHEMISTRY

What is Δ H for C₆H₁₂O₆(s) + 6O₂(g) -> 6CO₂(g) + 6H₂O(l) if Δ_f H°: C₆H₁₂O₆(s) = -1273 kJ/mol, CO₂(g) = -393.5 kJ/mol, H

Given: What is Δ H for C₆H₁₂O₆(s) + 6O₂(g) -> 6CO₂(g) + 6H₂O(l) if Δ_f H°: C₆H₁₂O₆(s) = -1273 kJ/mol, CO₂(g) = -393.5 kJ/mol, H₂O(l) = -285.8 kJ/mol? Formula: Δ_r H = [6(-393.5) + 6(-285.8)] - [-1273 + 0] = -2361 - 1714.8 + 1273 = -2802.8 kJ/mol.. Substitution: Substituting given values into formula as per NCERT 2026-27 method. Calculation: Simplifying step by step with proper SI units like m/s², J kg⁻¹ K⁻¹, 10⁻⁵, A m⁻¹ etc. Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII)Topic: Mole concept, atomic structure, chemical formulas like H₂O, CO₂, CH₃CH₂NH₂ and periodic trends.

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CHEMISTRY

Which compound is formed as a major product when propene reacts with HBr in the absence of peroxides?

According to Markovnikov’s rule, the major product is 2-bromopropane. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII)Topic: Mole concept, atomic structure, chemical formulas like H₂O, CO₂, CH₃CH₂NH₂ and periodic trends.

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CHEMISTRY

What is the electronic configuration of an element with 11 electrons?

Given: What is the electronic configuration of an element with 11 electrons? Formula: For 11 electrons (sodium): 1s² 2s² 2p⁶ 3s¹, following the order of filling based on increasing energy.. Substitution: Substituting given values into formula as per NCERT 2026-27 method. Calculation: Simplifying step by step with proper SI units like m/s², J kg⁻¹ K⁻¹, 10⁻⁵, A m⁻¹ etc. Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII)Topic: Mole concept, atomic structure, chemical formulas like H₂O, CO₂, CH₃CH₂NH₂ and periodic trends.

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CHEMISTRY

The K_a of formic acid ( HCOOH ) is 1.8 × 10⁻⁴. What is the pH of a 0.02 M solution?

Given: The K_a of formic acid ( HCOOH ) is 1.8 × 10⁻⁴. What is the pH of a 0.02 M solution? Formula: K_a = x²/0.02, 1.8 × 10⁻⁴= x²/0.02, x² = 3.6 × 10⁻⁶. Substitution & Calculation: x = √3.6 × 10⁻⁶approx 1.9 × 10⁻³, pH = -log(1.9 × 10⁻³) approx 2.72 . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII)Topic: Mole concept, atomic structure, chemical formulas like H₂O, CO₂, CH₃CH₂NH₂ and periodic trends.

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CHEMISTRY

In the reaction 2SO₂ + O₂ -> 2SO₃, how many grams of SO₃ are produced from 8 g of O₂ and excess SO₂? (Atomic masses: S =

Given: In the reaction 2SO₂ + O₂ -> 2SO₃, how many grams of SO₃ are produced from 8 g of O₂ and excess SO₂? (Atomic masses: S = 32, O = 16) Formula: Moles of O₂ = 8 / 32 = 0.25 mol. Substitution & Calculation: 1 mol O₂ produces 2 mol SO₃. Moles of SO₃ = 0.25 × 2 = 0.5 mol. Molar mass of SO₃ = 80 g/mol. Mass = 0.5 × 80 = 40 g. Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII)Topic: Mole concept, atomic structure, chemical formulas like H₂O, CO₂, CH₃CH₂NH₂ and periodic trends.

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