Answer:
The rate of reaction refers to how quickly or slowly the reactants disappear or the products appear in a given reaction. The rate of reaction depends on the concentration of the reactants. Thus, as concentration decreases with time, the rate of reaction decreases accordingly.
Therefore, reaction rates tend to decrease with time since the concentration of the reactants decrease with time as the reactants are being converted into products. Thus after three seconds, the rate would be lower, and the concentration of reactants would be lower.
