Concept:The rate of a reaction is defined as the change in concentration over a specific period of time.
Formula:$$ \text{Rate} = \frac{\text{Concentration}}{\text{Time}} $$
Solution:- The standard SI-derived unit for chemical concentration is moles per cubic decimeter (\( \text{mol dm}^{-3} \)).
- The standard unit for time is seconds (\( \text{s} \)).
- Dividing the two yields: \( \frac{\text{mol dm}^{-3}}{\text{s}} \).
- Using exponent rules to bring seconds to the numerator gives: \( \text{mol dm}^{-3} \text{s}^{-1} \), which is structurally represented in option D.
Why other options are incorrect:Option B represents \( \text{mol dm}^{3} \text{s}^{-1} \) (wrong sign on dm). Option A inverted the mole unit. Option C puts time in the numerator (\( \text{s} \) instead of \( \text{s}^{-1} \)).
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