Chemistry Reaction Kinetics UHS 2024
PMDC Verified Question 1 of 80
Identify the correct formula to calculate rate of reaction:
A
Change in concentration of substance ÷ Time taken for the change
B
Time taken for the change ÷ Change in concentration of substance
C
Time taken for the change ÷ Change in concentration of substance \( \times 100 \)
D
Time taken for the change \( \times \) Change in concentration of substance
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Change in concentration of substance ÷ Time taken for the change
Concept:

The rate of a chemical reaction quantifies the speed at which reactants are consumed or products are formed.

Formula:

$$ \text{Rate} = \pm \frac{\Delta C}{\Delta t} $$

Solution:

  • Mathematically, a rate is always a change in a measurable quantity divided by the time it took for that change to occur.
  • In chemistry, the quantity is the concentration of a substance.
  • Therefore, the correct verbal formula is: Change in concentration of substance ÷ Time taken for the change.


Why other options are incorrect:

Dividing time by concentration gives an inverted unit (s dm\(^3\) mol\(^{-1}\)). Multiplying them yields a nonsensical unit of concentration-time.

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