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Calculating reaction rates and gradients

The rate and extent of chemical change • Rate of reaction

Key concepts

What you'll likely be quizzed about

  • The mean rate is calculated by dividing the change in quantity (mass, volume, or concentration) by the time taken.
  • For reactants, the change is their decrease, while for products, the change is their increase.
  • Common units include g/s, cm³/s, or mol/s.
  • For example, if 12 cm³ of gas is produced in 30 seconds, the mean rate is calculated as 12 ÷ 30 = 0.40 cm³/s.
  • Ensuring consistent units and accurate time readings is crucial for correct calculations.

Flashcards

Test your knowledge with interactive flashcards

Effect of temperature on measured reaction rate

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Higher temperature increases particle energy and collision frequency, leading to higher rates.

Key notes

Important points to keep in mind

Mean rate = change in quantity ÷ time; ensure consistent units.

Choose measurement methods that match the species: mass, volume, or concentration.

Be clear with units: include the quantity unit and s⁻¹ (e.g., cm³/s or g/s).

For instantaneous rates, draw a clear tangent and use widely spaced points to calculate the gradient.

State if the calculated rate refers to reactant disappearance or product formation; note the sign convention.

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