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Rate of Reaction Summary
Rate of Reaction
Rate is a measure of the speed that a reaction takes place at. In other words it is a
measure of the change that happens in a single unit of time.
When measuring rate of a reaction we usually measure the amount of reactant used up
per unit of time or the amount of product produced per unit of time.
When measuring the amount of product produced, a syringe can be used if the product is
a gas. Alternatively, if the gas is allowed to escape during the reaction a measure of mass
lost could be used to measure the rate.
The rate changes throughout the reaction. It is greatest at the start, but gets less as
the reaction proceeds.
Changing the rate of reaction
Rate of reaction can be changed by:
1. Change in concentration of reactants
A reaction goes faster when the concentration of a reactant (acid) is increased as
there is more chance of a reactant particle colliding successfully with a different
2. Change in temperature
A reaction happens quicker at a higher temperature. When the temperature
increases by 10oC, the rate approximately doubles.
3. Change in surface area of reactants
Increasing the surface area of solid reactants increases the rate of a reaction. The
greater the surface area of a metal, the more of its particles exposed to the acid.
This increase in exposure increases the frequency of successful collisions.
4. Use of a catalyst.
Catalysts increase the rate of a reaction by lowering the activation energy
required for a successful collision. This means more successful collisions will take
place over a period of time.
A catalyst is a substance that changes the rate of a chemical reaction but
remains chemically unchanged.