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PUCET (Punjab) Chemical Kinetics — practice questions — page 2

Explore 80 free Chemical Kinetics questions in PUCET (Punjab) Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Chemical Kinetics questions and exercises with answers

Showing questions 31–60 of 80.

For a first-order reaction, rate ∝:Read the answer and worked solution →Units of rate constant k for a first-order reaction:Read the answer and worked solution →Arrhenius equation: k = A × e^(-Ea/RT). What is A?Read the answer and worked solution →For first-order reaction, half-life t₁/₂:Read the answer and worked solution →For zero-order reaction A → P, rate equals:Read the answer and worked solution →For first-order, integrated rate law:Read the answer and worked solution →For second-order reaction (single reactant), integrated rate law:Read the answer and worked solution →Catalyst affects:Read the answer and worked solution →Order of reaction CAN be determined from:Read the answer and worked solution →A first-order reaction is 25% complete in 20 min. Time for 75% completion:Read the answer and worked solution →For a reaction with Ea = 100 kJ/mol, find k₂/k₁ when T goes from 300 K to 350 K. (R = 8.314 J/mol K):Read the answer and worked solution →For a 2nd-order reaction with [A]₀ = 0.5 M and k = 0.1 L mol⁻¹ s⁻¹, half-life:Read the answer and worked solution →For complex reaction with rate-determining step that involves 2 molecules of A, the order in A is:Read the answer and worked solution →For Arrhenius plot of ln k vs 1/T, slope equals:Read the answer and worked solution →Threshold energy = Ea + average kinetic energy of reactants. If Ea = 50 kJ/mol and avg KE = 4 kJ/mol, threshold energy:Read the answer and worked solution →For reaction A → B with rate constant 10⁻³ s⁻¹ (first order), concentration after 1000 s if [A]₀ = 1 M:Read the answer and worked solution →A reaction has k = 0.05 s⁻¹. After how many seconds is 90% complete?Read the answer and worked solution →For radioactive decay (1st order), if 1/8 of initial nuclei remain, how many half-lives elapsed?Read the answer and worked solution →A catalyst lowers Ea from 100 kJ/mol to 75 kJ/mol at T = 300 K. Rate enhancement factor (R = 8.314 J/mol K):Read the answer and worked solution →For elementary bimolecular reaction 2 NO → products, rate law is:Read the answer and worked solution →Order vs molecularity: true or false?Read the answer and worked solution →Pick the order, fastRead the answer and worked solution →Drag each clue to its reaction orderRead the answer and worked solution →Knock out the kinetics mythsRead the answer and worked solution →Key in the kinetics numbersRead the answer and worked solution →Order or molecularity?Read the answer and worked solution →True or false: order and molecularityRead the answer and worked solution →Read the order off the rate lawRead the answer and worked solution →Complete the definition of orderRead the answer and worked solution →True or false: where a rate law comes fromRead the answer and worked solution →

Worked practice questions

For a first-order reaction, rate ∝:

  1. [A]⁰
  2. [A]¹
  3. [A]²
  4. [A]^0.5
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Correct answer: B. [A]¹

**First order:** rate = k[A]. **Examples:** radioactive decay, decomposition of H₂O₂. Half-life is constant (independent of initial concentration).

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Units of rate constant k for a first-order reaction:

  1. s⁻¹ (or min⁻¹)
  2. mol L⁻¹ s⁻¹
  3. L mol⁻¹ s⁻¹
  4. Dimensionless
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Correct answer: A. s⁻¹ (or min⁻¹)

**For 1st order:** rate has units mol L⁻¹ s⁻¹, [A] has mol L⁻¹, so k has units s⁻¹ (inverse time). **For 2nd order:** L mol⁻¹ s⁻¹. **For zero order:** mol L⁻¹ s⁻¹.

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Arrhenius equation: k = A × e^(-Ea/RT). What is A?

  1. Activation energy
  2. Pre-exponential or 'frequency' factor
  3. Equilibrium constant
  4. Temperature
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Correct answer: B. Pre-exponential or 'frequency' factor

A is the frequency factor (or Arrhenius prefactor): accounts for collision frequency and orientation. Has same units as k. Often only weakly T-dependent compared to exp term.

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