Different reactions happen at different speeds. Reactions that occur slowly have a low reaction rate and reactions that occur quickly have a fast reaction rate.
An example of a slow reaction is the chemical weathering of rocks and an example of a fast reaction is an explosion.
There are 2 ways to measure the reaction rate - The first one is that you measure how quickly or slowly the reactant is used up and the second way is to measure how quickly or slowly the product is produced.

RATE OF REACTION = AMOUNT OF REACTANT USED OR AMOUNT OF PRODUCT FORMED divided by TIME TAKEN.
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