CHEMISTRY

CHEMISTRY

What is the degree of dissociation of 0.01 M acetic acid if its molar conductivity is 39.05 S cm² mol⁻¹ and Lambda_m

Given: What is the degree of dissociation of 0.01 M acetic acid if its molar conductivity is 39.05 S cm² mol⁻¹ and Lambda_m⁰ = 390.5 S cm² mol^{-1 ? These values define the system as per NCERT data. Formula: α = Lambda_m/Lambda_m⁰ = 39.05/390.5 = 0.1 .. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Substituting values like 1.2 × 10⁻⁵, 236 J kg⁻¹ K⁻¹, CH₃CH₂NH₂ etc. into the formula and simplifying step by step. 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: Relevant Chemistry topic covering principles and examples as per NCERT.

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CHEMISTRY

A solution is made by mixing 30 mL of methanol ( CH₃OH ) and 70 mL of water, with a total volume of 95 mL. What is the

Given: A solution is made by mixing 30 mL of methanol ( CH₃OH ) and 70 mL of water, with a total volume of 95 mL. What is the volume percentage of methanol? (Density of methanol = 0.792 g/mL) These values define the system as per NCERT data. Formula: Volume % = fracVolume of methanolTotal volume × 100. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Given volume of methanol = 30 mL, total volume = 95 mL. Volume % = 30/95 × 100 = 31.58% . 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: Solutions, Topic: Concentration terms and colligative properties.

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CHEMISTRY

A reaction’s rate increases by a factor of 8 when [A] is doubled and [B] is doubled. If the order with respect to B is

Given: A reaction’s rate increases by a factor of 8 when [A] is doubled and [B] is doubled. If the order with respect to B is 1, what is the order with respect to A? These values define the system as per NCERT data. Formula: Rate = k[A]^n[B]^m, m = 1, 8 = 2^n × 2¹. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: 8 = 2^{n+1, n + 1 = 3, n = 2 . 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: Relevant Chemistry topic covering principles and examples as per NCERT.

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CHEMISTRY

The maximum oxidation state of cobalt (Co, Z = 27) observed in its compounds is:

Co shows +2, +3, and +4, with +4 being the maximum (e.g., in CoOâ‚‚ ), though +3 is more common. 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

How many sigma bonds are present in the Câ‚‚Hâ‚‚ molecule?

Câ‚‚Hâ‚‚ has a triple bond (1 sigma, 2 pi) between carbons and 2 single bonds (2 sigma) to hydrogens. Total sigma bonds = 1 + 2 = 3. 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 number of hydrogen bonds between adenine and thymine in DNA is:

Adenine pairs with thymine via two hydrogen bonds in DNA, contributing to the stability of the double helix. 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

What is the number of unpaired electrons in [FeF₆]^{3- ?

Given: What is the number of unpaired electrons in [FeF₆]^{3- ? These values define the system as per NCERT data. Formula: Fe³⁺ ( d⁵ ) with weak field F^- in an octahedral field is high spin ( t_{2g³ e_g² ), with 5 unpaired electrons.. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Substituting values like 1.2 × 10⁻⁵, 236 J kg⁻¹ K⁻¹, CH₃CH₂NH₂ etc. into the formula and simplifying step by step. 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 pH of a 0.004 M Ca(OH)2 solution, assuming complete dissociation?

Given: What is the pH of a 0.004 M Ca(OH)2 solution, assuming complete dissociation? These values define the system as per NCERT data. Formula: [OH-] = 2 × 0.004 = 0.008 M, pOH = -log(0.008) approx 2.1. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: pH = 14 - 2.1 = 11.9 . 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: Solutions, Topic: Concentration terms and colligative properties.

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CHEMISTRY

Which complex has a tetrahedral geometry?

[MnBr₄]^{2- (Mn²⁺, 4 ligands) adopts tetrahedral geometry due to sp³ hybridization with weak field Br^-, unlike the octahedral or square planar options.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Chemical Bonding and Molecular Structure, Topic: Bonding theories, VSEPR and hybridization.

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CHEMISTRY

For the reaction Nâ‚‚(g) + 2Oâ‚‚(g) 2NOâ‚‚(g), K_c = 0.04 at 500 K. If initial concentrations are [Nâ‚‚] = 0.2 M and [Oâ

Given: For the reaction N₂(g) + 2O₂(g) 2NO₂(g), K_c = 0.04 at 500 K. If initial concentrations are [N₂] = 0.2 M and [O₂] = 0.3 M, what is [NO₂] at equilibrium? These values define the system as per NCERT data. Formula: Let [NO₂] = 2x, then [N₂] = 0.2 - x, [O₂] = 0.3 - 2x. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: K_c = frac[NO₂]²[N₂][O₂]² = (2x)²/(0.2 - x)(0.3 - 2x)² = 0.04 . Simplify: 4x² = 0.04 (0.2 - x)(0.3 - 2x)², solve: x approx 0.015, 2x approx 0.03 M. 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: Thermodynamics, Equilibrium and Chemical Kinetics, Topic: Energetics, equilibrium constants and reaction rates.

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CHEMISTRY

A reaction has k = 6.0 × 10⁻⁶ s^{-1 at 300 K and E_a = 50 kJ mol^{-1 . What is the pre-exponential factor A in s^{-

Given: A reaction has k = 6.0 × 10⁻⁶ s^{-1 at 300 K and E_a = 50 kJ mol^{-1 . What is the pre-exponential factor A in s^{-1 ? (R = 8.314 J/mol · K) These values define the system as per NCERT data. Formula: k = A e^{-E_a/RT. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: 6.0 × 10⁻⁶= A e^{-50000/(8.314 × 300), A = 6.0 × 10⁻⁶/ e^{-20.06 = 3.2 × __10POW₃__. 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: Relevant Chemistry topic covering principles and examples as per NCERT.

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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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