A first-order reaction is 25% complete in 15 minutes. What is the rate constant?
k = (2.303/15) log(1/0.75) ≈ 0.0192 min⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Pseudo First Order and Complex Reactions
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A first-order reaction is 40% complete in 15 minutes. What is the rate constant?
k = (2.303/15) log(1/0.6) ≈ 0.0341 min⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Pseudo First Order and Complex Reactions
A first-order reaction is 25% complete in 10 minutes. What is the rate constant?
k = (2.303/10) log(1/0.75) ≈ 0.0288 min⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Pseudo First Order and Complex Reactions
A first-order reaction has a half-life of 18 minutes. What fraction of the reactant remains after 54 minutes?
3 half-lives → fraction remaining = 1/8.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Pseudo First Order and Complex Reactions
A first-order reaction has a rate constant of 0.0173 min⁻¹. What is the time for 80% completion?
t = (2.303/0.0173) log 5 ≈ 93 min.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Pseudo First Order and Complex Reactions
In Kjeldahl’s method, 0.5 g of an organic compound produced ammonia that neutralized 20 mL of 0.1 M H₂SO₄. What is the p
Moles of H₂SO₄ = 0.02 × 0.1 = 0.002. Moles of NH₃ = 0.004 (2H per H₂SO₄). Mass of N = 0.004 × 14 = 0.056 g. Percentage = (0.056/0.5) × 100 = 11.2%.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Isomerism - Structural Isomerism - Chain Position Functional Metamerism
How many significant figures are present in the result of (0.0456 × 298.15)/0.112?
0.0456 (3 sig figs), 298.15 (5 sig figs), 0.112 (3 sig figs). Result ≈ 121.36; limited to 3 sig figs (121).
Ref: NCERT Class 11 Chemistry > Chapter 1: Some Basic Concepts of Chemistry > Topic: Stoichiometry and Stoichiometric Calculations and Limiting Reagent
How many significant figures are present in the result of (0.0567 × 273.15)/0.0821?
0.0567 (3 sig figs), 273.15 (5 sig figs), 0.0821 (3 sig figs). Result ≈ 188.56; limited to 3 sig figs (189).
Ref: NCERT Class 11 Chemistry > Chapter 1: Some Basic Concepts of Chemistry > Topic: Reactions in Solutions and Mass Percentage and Numericals