Worksheet: First-Order Integrated Rate Laws

In this worksheet, we will practice using the integrated rate law for a first-order reaction to calculate the rate constant and initial concentration.

Q1:

The decomposition of cyclobutane is a first-order reaction with a rate constant of 9 . 2 0 × 1 0 3 s−1 at 5 0 0 C . Calculate, to 2 significant figures, the time taken for 80.0% of a sample of cyclobutane to decompose.

Q2:

Iodine-131 decays by 𝛽 emission with a rate constant of 0.138 d−1: Calculate, to 2 significant figures, the time taken for 90.0% of a sample of iodine-131 to decay.

Q3:

Nitric oxide from aircraft exhaust reacts with atmospheric ozone, contributing to the depletion of the ozone layer, as shown in the equation. This reaction is of the first order with respect to both reactants and has a rate constant of 2 . 2 0 × 1 0 L/mol⋅s. What is the instantaneous rate of reaction of N O if [ N O ] = 3 . 3 0 × 1 0 M and [ O ] 3 = 5 . 9 0 × 1 0 M? Give your answer to two significant figures.

  • A 2 . 4 × 1 0 mol/L⋅s
  • B 3 . 3 × 1 0 mol/L⋅s
  • C 7 . 7 × 1 0 mol/L⋅s
  • D 4 . 3 × 1 0 mol/L⋅s
  • E 2 . 5 × 1 0 mol/L⋅s

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