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Investigating concentration effects on reaction rate

The rate and extent of chemical change • Rate of reaction

Key concepts

What you'll likely be quizzed about

  • Higher concentration increases the number of reactant particles per unit volume.
  • This raised particle density increases the frequency of successful collisions between reacting particles.
  • Higher collision frequency results in a higher reaction rate because more collisions lead to more successful product-forming events per unit time.
  • Concentration changes alter the initial slope of time-based measurements, where higher concentration generates steeper initial slopes on volume-time or absorbance-time graphs, indicating faster rates.
  • In contrast, lower concentration produces shallower slopes and slower rates.

Flashcards

Test your knowledge with interactive flashcards

What measurement best indicates initial rate in gas evolution experiments?

Click to reveal answer

The earliest linear portion of the volume-time graph gives the best estimate of initial rate.

Key notes

Important points to keep in mind

Increase in concentration raises collision frequency, producing a higher rate.

Use a gas syringe for accurate volume-time data; check for leaks and friction.

Use a colorimeter for precise colour measurements; ensure consistent wavelength and blanks.

Monitor turbidity with fixed geometry and controlled light for repeatable readings.

Keep temperature, surface area, and catalysts constant while varying concentration.

Calculate rate as the change in measured quantity divided by time (Δquantity/Δtime).

Estimate initial rate from the early linear region or tangent at time zero.

Repeat trials and average initial rates to reduce random error.

Account for gas solubility and side reactions when interpreting gas-evolution results.

Use dilution to slow very fast reactions or employ automated logging for rapid data collection.

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