The concentration of reactants directly affects the rate of a chemical reaction.
Key points:
- Higher concentration → faster reaction:
- More reactant particles are present, so collisions occur more frequently, increasing the reaction rate.
- Lower concentration → slower reaction:
- Fewer reactant particles lead to fewer collisions, decreasing the reaction rate.
- Depends on reaction order:
- For a reaction that is first-order with respect to a reactant, the rate is directly proportional to its concentration.
- For a second-order reaction, the rate is proportional to the square of the concentration.
Example:
- For A + B → C, doubling the concentration of A often doubles the rate if the reaction is first-order with respect to A.
In short: More particles → more collisions → faster reaction; fewer particles → slower reaction.