A first-order reaction is 20% complete in 12 minutes. What is the rate constant?
k = (2.303/12) log(1/0.8) ≈ 0.0186 min⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
Order and Molecularity and Units of Rate Constant
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A second-order reaction has a rate constant of 0.5 L mol⁻¹ min⁻¹. If the initial concentration is 0.2 mol L⁻¹, what is t
t½ = 1/(0.5×0.2) = 10 min.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A first-order gaseous reaction has an initial pressure of 1.2 atm. After 50 s, the total pressure is 1.6 atm. What is th
x = 0.4, pA = 0.8. k ≈ 0.0081 s⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
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 first-order reaction has a rate constant of 0.0462 min⁻¹. What is the time required for 75% completion?
t = (2.303/0.0462) log 4 ≈ 30 min.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
A first-order reaction has an initial concentration of 0.5 mol L⁻¹ and a rate constant of 0.0693 min⁻¹. What is the conc
[R] = 0.5 / 4 = 0.125 mol L⁻¹.
Ref: NCERT Class 12 Chemistry > Chapter 3: Chemical Kinetics > Topic: Order and Molecularity and Units of Rate Constant
For the reaction 3A → 2B, the rate of formation of B is 0.02 mol L⁻¹ s⁻¹. What is the rate of disappearance of A?
−Δ[A]/Δt = 3 × (0.02/2) = 0.03 mol L⁻¹ s⁻¹.
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 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