Half life period of first order reaction is 20 minutes. How long will it take to 75% completion?
40 minutes correct as per chemistry principle.
Ref: NCERT Chemistry Class XII — Chemical Kinetics and Surface Chemistry
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A first-order reaction has a half-life of 25 minutes. What percentage of the reactant remains after 75 minutes?
3 half-lives → fraction remaining = 1/8 = 12.5%.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Temperature Dependence - Arrhenius Equation and Activation Energy
A zero-order reaction has a rate constant of 5.0 × 10⁻³ mol L⁻¹ min⁻¹. If the initial concentration is 0.25 mol L⁻¹, how
t = (0.25 − 0.1)/(5.0×10⁻³) = 30 min.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Rate of Reaction - Average and Instantaneous Rate and Rate Law
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
A zero-order reaction takes 90 s to reduce the concentration from 0.15 mol L⁻¹ to 0.06 mol L⁻¹. What is the rate constan
k = (0.15 − 0.06)/90 = 1.0 × 10⁻³ mol L⁻¹ s⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Pseudo First Order and Complex Reactions
A first-order reaction is 50% complete in 40 minutes. What is the time required for 90% completion?
k = 0.693/40. t₉₀ = (2.303/k) log 10 ≈ 133 min.
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 12 minutes. What is the time required for 90% completion?
k = 0.693/12 ≈ 0.05775 min⁻¹. For 90% completion t = (2.303/k) log 10 ≈ 40 min.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Pseudo First Order and Complex Reactions
A zero-order reaction has a rate constant of 2.0 × 10⁻³ mol L⁻¹ min⁻¹. If the initial concentration is 0.1 mol L⁻¹, how
t = (0.1 − 0.06)/(2.0×10⁻³) = 20 min.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A zero-order reaction has a rate constant of 8.0 × 10⁻⁴ mol L⁻¹ s⁻¹. How long will it take for the concentration to decr
t = (0.16 − 0.04)/(8.0×10⁻⁴) = 150 s.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A second-order reaction has a rate constant of 0.07 L mol⁻¹ s⁻¹ and an initial concentration of 0.25 mol L⁻¹. What is th
t = (1/0.05 − 1/0.25)/0.07 ≈ 228.57 s.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A reaction follows zero-order kinetics with a rate constant of 4.0 × 10⁻⁴ mol L⁻¹ s⁻¹. If the initial concentration is 0
t = [R]₀/k = 0.08/(4.0×10⁻⁴) = 200 s.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Integrated Rate Equations - Zero Order Reactions
A zero-order reaction has a rate constant of 6.0 × 10⁻³ mol L⁻¹ min⁻¹. If the initial concentration is 0.18 mol L⁻¹, how
t = ([R]₀ − [R])/k = (0.18 − 0.12)/(6.0×10⁻³) = 10 min.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Collision Theory - Effective Collisions and Catalyst Effect
