Average rate

Definition

The average rate of a chemical reaction is the change in concentration of a reactant or product per unit time over a specific time interval. It gives an overall sense of how quickly the reaction proceeds during that period.

5 Must Know Facts For Your Next Test

1. The average rate can be calculated using the formula: $\text{Average Rate} = \frac{\Delta [\text{Reactant or Product}]}{\Delta t}$, where $\Delta$ signifies change and $t$ is time.
2. It is typically expressed in units such as Molarity per second (M/s).
3. Average rate decreases as the reaction progresses due to the consumption of reactants.
4. In a graph of concentration versus time, the average rate corresponds to the slope of the line connecting two points on the curve.
5. For reactions with multiple steps, each step has its own average rate and these can vary significantly.

Review Questions

• How do you calculate the average rate of a reaction?
• What units are commonly used for expressing the average rate?
• Why does the average rate generally decrease as a reaction proceeds?

Related terms

Instantaneous Rate: The instantaneous rate is the change in concentration at a specific moment in time, typically determined by taking the derivative of concentration with respect to time.

Rate Law: A mathematical expression that describes the relationship between the concentrations of reactants and the reaction rate.

Reaction Order: An exponent in the rate law that indicates how sensitive the reaction rate is to changes in reactant concentration.