For a first-order reaction, how many half-lives are required for 75% completion?
25% remains = (1/2)² → 2 half-lives.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Pseudo First Order and Complex Reactions
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A reaction’s rate increases by 27 times when the concentration of the reactant is increased by 3 times. What is the orde
3ⁿ = 27 → n = 3.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A reaction has a rate constant with units mol⁻¹ L s⁻¹. What is the order of the reaction?
Unit matches second-order.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A first-order reaction has a rate constant of 0.0462 min⁻¹. What percentage of the reactant remains after 15 minutes?
log([R]₀/[R]) ≈ 0.301 → % remaining = 50%.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A zero-order reaction reduces the concentration from 0.18 mol L⁻¹ to 0.09 mol L⁻¹ in 45 s. What is the rate constant?
k = 0.09/45 = 2.0 × 10⁻³ mol L⁻¹ s⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A first-order reaction has a half-life of 18 minutes. What percentage of the reactant remains after 54 minutes?
3 half-lives → % remaining = 12.5%.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A reaction has the rate law Rate = k[A][B]². If the concentration of A is tripled and B is halved, what happens to the r
New rate = (3/4) × initial rate.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Integrated Rate Equations - Zero Order Reactions
A second-order reaction has a rate constant of 0.06 L mol⁻¹ s⁻¹. If the initial concentration is 0.2 mol L⁻¹, what is th
t = (1/0.08 − 1/0.2)/0.06 = 125 s.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Integrated Rate Equations - Zero Order Reactions
A first-order gaseous reaction has an initial pressure of 2.4 atm. After 40 s, the total pressure is 3.0 atm. What is th
x = 0.6, pA = 1.8. k ≈ 0.0072 s⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Integrated Rate Equations - Zero Order Reactions
For the reaction A + 2B → 3C, the rate of formation of C is 0.15 mol L⁻¹ s⁻¹. What is the rate of disappearance of B?
−Δ[B]/Δt = 2 × (0.15/3) = 0.1 mol L⁻¹ s⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Integrated Rate Equations - Zero Order Reactions
A zero-order reaction takes 120 s to reduce the concentration from 0.3 mol L⁻¹ to 0.18 mol L⁻¹. What is the rate constan
k = (0.3 − 0.18)/120 = 1.0 × 10⁻³ mol L⁻¹ s⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Integrated Rate Equations - Zero Order Reactions
A first-order reaction has a half-life of 15 minutes. What percentage of the reactant decomposes in 45 minutes?
3 half-lives → % decomposed = 87.5%.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Integrated Rate Equations - Zero Order Reactions