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CHEMISTRY

Chemistry questions here cover the three main branches: physical chemistry with its calculations, organic chemistry reactions and mechanisms, and inorganic chemistry including periodic trends and bonding. Practise by topic or sit a full test to see how well the concepts hold up under time pressure.

45 questions

CHEMISTRY

For Nâ‚‚(g) + Oâ‚‚(g) 2NO(g), K_c = 0.02 at 1500 K. What is K_c for NO(g) 1/2 Nâ‚‚(g) + 1/2 Oâ‚‚(g) ?

Given: For N₂(g) + O₂(g) 2NO(g), K_c = 0.02 at 1500 K. What is K_c for NO(g) 1/2 N₂(g) + 1/2 O₂(g) ? These values define the system as per NCERT data. Formula: For the reverse halved reaction, K_c' = frac1sqrtK_c = frac1sqrt0.02 approx 7.07 .. 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 of two volatile liquids A and B has a total vapor pressure of 280 mm Hg. If the vapor pressure of pure A is 4

Given: A solution of two volatile liquids A and B has a total vapor pressure of 280 mm Hg. If the vapor pressure of pure A is 400 mm Hg and that of pure B is 160 mm Hg, what is the mole fraction of B in the solution? These values define the system as per NCERT data. Formula: Using Raoult's law: p_{total = x_A p_A⁰ + x_B p_B⁰, where x_A + x_B = 1. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: 280 = (1 - x_B) · 400 + x_B · 160 . 280 = 400 - 400 x_B + 160 x_B . 280 = 400 - 240 x_B, 240 x_B = 120, x_B = 0.5 . 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

A first-order reaction has a rate constant of 0.01386 min^{-1 . What percentage of the reactant remains after 100 minute

Given: A first-order reaction has a rate constant of 0.01386 min^{-1 . What percentage of the reactant remains after 100 minutes? These values define the system as per NCERT data. Formula: ln frac[R]_0[R] = k t = 0.01386 × 100 = 1.386. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: frac[R][R]_0 = e^{-1.386 = 0.25, so 25% remains. 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

How many optical isomers are possible for [Co(NH₃)2(en)2]^{3+ ?

[Co(NH₃)2(en)2]^{3+ is octahedral with two bidentate en ligands and lacks symmetry in its cis form, forming 2 optical isomers (d and l). 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

How many moles of electrons are required to reduce 1 mol of Cr³⁺ to Cr(s)?

Given: How many moles of electrons are required to reduce 1 mol of Cr³⁺ to Cr(s)? These values define the system as per NCERT data. Formula: Reaction: Cr³+ + 3e- -> Cr(s). This is the standard NCERT relation for this phenomenon. Substitution & Calculation: 3 moles of electrons are required per mole of Cr³⁺. 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 first-order reaction has a rate constant of 0.01732 min^{-1 . What is the half-life in minutes?

Given: A first-order reaction has a rate constant of 0.01732 min^{-1 . What is the half-life in minutes? These values define the system as per NCERT data. Formula: t_{1/2 = 0.693/k = 0.693/0.01732 = 40 min .. 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

Which complex is diamagnetic?

[Pt(CN)4]^{2- (Pt²⁺, d⁸ ) with strong field CN^- in a square planar geometry is low spin, with 0 unpaired electrons, making it diamagnetic. 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

For the reaction 2CO(g) + Oâ‚‚(g) 2COâ‚‚(g), K_c = 25 at 1000 K. If initial concentrations are [CO] = 0.2 M and [Oâ‚‚] =

Given: For the reaction 2CO(g) + O₂(g) 2CO₂(g), K_c = 25 at 1000 K. If initial concentrations are [CO] = 0.2 M and [O₂] = 0.1 M, what is [CO₂] at equilibrium? These values define the system as per NCERT data. Formula: Let [CO₂] = 2x, then [CO] = 0.2 - 2x, [O₂] = 0.1 - x. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: K_c = frac[CO₂]²[CO]² [O₂] = (2x)²/(0.2 - 2x)² (0.1 - x) = 25 . Assume x approx 0.1 (near completion), adjust: 2x approx 0.18 M (simplified). 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

Calculate the heat required to raise the temperature of 40 g of ethanol from 25°C to 35°C (specific heat of ethanol =

Given: Calculate the heat required to raise the temperature of 40 g of ethanol from 25°C to 35°C (specific heat of ethanol = 2.46 J/g · K). These values define the system as per NCERT data. Formula: q = m × c × Δ T. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: m = 40 g, c = 2.46 J/g · K, Δ T = 35 - 25 = 10 K. q = 40 × 2.46 × 10 = 984 J = 0.984 kJ. 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

What is the bond angle in NH₃ molecule?

NH₃ has a tetrahedral electron pair geometry (3 bonds, 1 lone pair), but lone pair repulsion reduces the bond angle to 107°. 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 heat released when 44 g of propane (C₃H₈) burns completely? (Δ H° = -2219.85 kJ/mol, molar mass = 44 g

Given: What is the heat released when 44 g of propane (C₃H₈) burns completely? (Δ H° = -2219.85 kJ/mol, molar mass = 44 g/mol) These values define the system as per NCERT data. Formula: Moles = 44 / 44 = 1 mol. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Heat = 1 × 2219.85 = 2219.85 kJ. 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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