The rate of reaction is the speed at which reactants are converted into products. It is measured as the change in concentration of a reactant or product per unit time.
Factors Affecting the Rate of Reaction
- Concentration: higher concentration of reactants → more particles → faster reaction.
- Temperature: higher temperature → particles move faster and collide more often with more energy → faster reaction.
- Surface area: smaller particle size (larger surface area) → faster reaction.
- Pressure (for gases): higher pressure → faster reaction.
- Catalyst: speeds up the reaction without being used up.
Collision Theory
For a reaction to occur, particles must collide with enough energy (the activation energy) and with the correct orientation. Anything that increases the frequency of effective collisions increases the reaction rate.
Catalysts
A catalyst increases the rate of a reaction by lowering the activation energy, without being consumed. Biological catalysts are called enzymes.
Summary
The rate of reaction increases with higher concentration, temperature, surface area and pressure, and with the use of a catalyst. Collision theory explains these effects through the frequency and energy of particle collisions.
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