Answer:
speed at which product is formed
Step-by-step explanation:
The rate of a reaction is defined as the speed at which product is formed. The primary aim of a chemical reaction is to obtain a product and hence it's rate of formation is usually expressed as product per unit time.
A further proof for this is in the knowledge of factors that affect the rate of chemical reaction. These factors are generally used industrially to increase the rate of chemical reaction. For example, addition of catalyst.
Addition of catalyst is used to increase the rate of chemical reaction by reducing the reaction's activation energy. Activation energy is the minimum amount of energy that must be overcome for a reaction to occur. Catalyst is thus added to get more products in the shortest possible time by reducing the activation energy of the reaction. From this illustration, we can see that the rate of reaction is increased in order to make more products and NOT for reactants to disappear.