rate definition

Question

For reaction: A → Products, rate expression in terms of A is:

RankGuru · Accepted Answer

1. **Definition of Rate**: The speed at which a chemical reaction proceeds, expressed as the change in concentration per unit time.
2. **Reactants**: Since reactant $A$ is being consumed, its concentration $[A]$ decreases over time. Therefore, $\frac{d[A]}{dt}$ will be a negative value.
3. **Sign Convention**: Reaction rates are always expressed as positive quantities. 
4. **Rate expression**: To make the rate of consumption of $A$ positive, we introduce a negative sign: **$-\frac{d[A]}{dt}$**.
5. **Unit**: Usually $mol \, L^{-1} \, s^{-1}$.

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rate definition

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