What happens to the rate of most reactions as the reaction progresses?

the rate change depends on the energy change of the reaction.
the rate decreases as the concentration of the reactants decreases.
the rate increases as the concentration of the products increases.
the rate remains constant over the course of the reaction.

The rate decreases as the concentration of the reactants decreases.

Explanation:

The measurement of the reaction rate is based on the disappearance of a reactant or appearance of a product with increasing reaction time.

During a reaction, the concentration of a reactant decreases exponentially with time while that of a product increases exponentially with time. This is because a reactant is consumed in a reaction while products builds in that same reaction.

The reaction rate therefore is directly proportional to the concentration of the reactants.

The rate decreases as the concentration of the reactions decreases.

Explanation: