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#physical chemistry

74 public questions tagged with this topic.

CHEMISTRY

A solution of 2.44 g of acetic acid ( CH₃COOH ) in 100 g of benzene shows a freezing point depression of 0.5 K. If the

Given: A solution of 2.44 g of acetic acid ( CH₃COOH ) in 100 g of benzene shows a freezing point depression of 0.5 K. If the molar mass is 60 g/mol, what is the van't Hoff factor due to dimerization? ( K_f = 5.12 K kg/mol ) These values define the system as per NCERT data. Formula: Molality = 2.44 / 60/0.1 = 0.4067 mol/kg. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Normal Δ T_f = 5.12 × 0.4067 = 2.08 K . Observed Δ T_f = 0.5 K . i = 0.5/2.08 = 0.24 . 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

The Henry's law constant for a gas in water is 8 × __10POW₃__bar at 298 K. What is the mole fraction of the gas under

Given: The Henry's law constant for a gas in water is 8 × __10POW₃__bar at 298 K. What is the mole fraction of the gas under a partial pressure of 0.4 bar? These values define the system as per NCERT data. Formula: p = K_H · x. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: 0.4 = 8 × __10POW₃__ · x . x = 0.4/8 × __10POW₃__= 5 × 10⁻⁵. 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

For the reaction CO(g) + 2H₂(g) -> CH₃OH(l), if Δ H = -128.1 kJ/mol at 298 K, what is Δ U (R = 8.314 J/mol · K)?

Given: For the reaction CO(g) + 2H₂(g) -> CH₃OH(l), if Δ H = -128.1 kJ/mol at 298 K, what is Δ U (R = 8.314 J/mol · K)? Formula: Δ n_g = 0 - (1 + 2) = -2, RT = 8.314 × 298 / 1000 = 2.48 kJ. Substitution & Calculation: Δ H = Δ U + Δ n_g RT. Δ U = -128.1 - (-2 × 2.48) = -123.14 kJ/mol. 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 zero-order reaction has a rate constant of 7.0 × 10⁻³ mol L^{-1 s^{-1 . What is the half-life if the initial conce

Given: A zero-order reaction has a rate constant of 7.0 × 10⁻³ mol L^{-1 s^{-1 . What is the half-life if the initial concentration is 0.28 M? These values define the system as per NCERT data. Formula: For zero order, t_{1/2 = frac[R]_02k = frac0.282 × 7.0 × 10⁻³= 20 s .. 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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PHYSICS

What is the molar specific heat capacity at constant pressure for a diatomic gas if C_v = 5/2 R and R = 8.3 J mol^{-1 K^

Given: What is the molar specific heat capacity at constant pressure for a diatomic gas if C_v = 5/2 R and R = 8.3 J mol^{-1 K^{-1 ? These values define the system as per NCERT data. Formula: C_p - C_v = R. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: C_p = C_v + R = 5/2 R + R = 7/2 R . C_p = 7/2 × 8.3 = 29.05 J mol^{-1 K^{-1 . 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 Physics Textbook for Class XI and XII, Chapter: Dual Nature, Atoms, Nuclei and Electronic Devices, Topic: Atomic structure, nuclear binding and semiconductor physics.

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CHEMISTRY

What is the molar conductivity at infinite dilution for MgSO₄ if the ionic molar conductivities of Mg²⁺ and SO₄²

Given: What is the molar conductivity at infinite dilution for MgSO₄ if the ionic molar conductivities of Mg²⁺ and SO₄²⁻ are 106.0 S cm² mol⁻¹ and 160.0 S cm² mol⁻¹ respectively? These values define the system as per NCERT data. Formula: Kohlrausch’s law: Lambda_m⁰ = lambda_{Mg^{2+⁰ + lambda_{SO_4^{2-⁰. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Lambda_m⁰ = 106.0 + 160.0 = 266.0 S cm² mol^{-1 . 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 of 4.8 g of a non-volatile solute in 150 g of water has a boiling point elevation of 0.208 K. What is the mol

Given: A solution of 4.8 g of a non-volatile solute in 150 g of water has a boiling point elevation of 0.208 K. What is the molar mass of the solute? ( K_b = 0.52 K kg/mol ) These values define the system as per NCERT data. Formula: Molality = Δ T_b/K_b = 0.208/0.52 = 0.4 mol/kg. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Moles = 0.4 × 0.15 = 0.06 mol . Molar mass = 4.8/0.06 = 80 g/mol . 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

How many grams of ethylene glycol ( C₂H₆O₂ ) are required to depress the freezing point of 300 g of water by 1.24

Given: How many grams of ethylene glycol ( C₂H₆O₂ ) are required to depress the freezing point of 300 g of water by 1.24 K? ( K_f = 1.86 K kg/mol, Molar mass of ethylene glycol = 62 g/mol ) These values define the system as per NCERT data. Formula: Δ T_f = K_f · m. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: 1.24 = 1.86 · m, m = 0.667 mol/kg . Moles = 0.667 × 0.3 = 0.2 mol . Mass = 0.2 × 62 = 12.4 g . 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

A solution of 12 g of a non-volatile solute in 100 g of water boils at 100.52°C at 1 atm. What is the molar mass of the

Given: A solution of 12 g of a non-volatile solute in 100 g of water boils at 100.52°C at 1 atm. What is the molar mass of the solute? ( K_b = 0.52 K kg/mol ) These values define the system as per NCERT data. Formula: Δ T_b = 100.52 - 100 = 0.52 K. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Molality = 0.52/0.52 = 1 mol/kg . Moles = 1 × 0.1 = 0.1 mol . Molar mass = 12/0.1 = 120 g/mol . 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

Which of the following has the highest boiling point?

Boiling points increase with the size and molecular mass of halogen atoms in halogenated hydrocarbons. This follows from NCERT principle where relation explains outcome clearly for students.

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

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