Factors Affecting the Rate of Reaction
Science: KS3, topic 2.7.4
Rate of Reaction - Key Factors
The main factors that affect the rate of chemical reactions are:
Concentration of reactants
- Increasing the concentration increases the collision frequency.
- The increased collision frequency increases the rate of reaction.
Pressure of gas reactants
- Increasing pressure is like increasing the concentration.
- Increasing pressure increases the collision frequency.
- The increased collision frequency increases the rate of reaction.
Temperature
- Increasing the temperature increases the collision rate.
- Increasing the temperature increases reactant particle energy.
- More particles have energy greater than the activation energy needed.
Successful collisions
- Together, the increased collision rate and particle energy lead to more successful collisions.
- The increased number of successful collisions increases the rate of reaction.
Surface area of solid reactants
- Increasing surface area increases collision frequency.
- Breaking solids into smaller lumps (e.g. powders) increases surface area.
Surface area to volume ratio
- The increased surface area to volume ratio exposes more particles to attack.
Catalysts
- Catalysts are substances that increase a chemical reaction's rate.
- Catalysts do not reduce in quantity during the reaction.
Test yourself on Factors Affecting the Rate of Reaction
Limestone and marble structures crumble when reacted with acid. How will an increase in the concentration of acid in rainwater affect the rate at which limestone and marble are worn away?
Two identical reactions between a metal and dilute acid are set up. Experiment 1 uses acid with a concentration of 0.5 mol/dm³. Experiment 2 uses acid with a concentration of 2 mol/dm³. All other conditions are the same. Which experiment will reach completion fastest?