Changing the concentration of reactants in a chemical reaction can significantly affect the reaction rate and sustainability of the reaction. According to the collision theory, the reaction rate depends on the frequency of effective collisions between reactant molecules. When the concentration of reactants is increased, there are more molecules present in the reaction mixture, leading to a higher probability of effective collisions and thus an increased reaction rate.The effect of changing the concentration of reactants on the reaction rate can be described by the rate law, which is an equation that relates the reaction rate to the concentrations of reactants raised to certain powers called the reaction orders. The rate law is usually expressed as:Rate = k[A]^m[B]^nwhere Rate is the reaction rate, k is the rate constant, [A] and [B] are the concentrations of reactants A and B, and m and n are the reaction orders with respect to A and B, respectively.As for the sustainability of a chemical reaction, increasing the concentration of reactants can lead to a longer-lasting reaction, as there are more reactant molecules available to be converted into products. However, it is important to note that the sustainability of a reaction is also influenced by other factors, such as the reaction mechanism, the presence of catalysts, and the reaction conditions e.g., temperature, pressure .In summary, increasing the concentration of reactants generally leads to an increased reaction rate and can contribute to the sustainability of a chemical reaction, but other factors must also be considered to fully understand the behavior of a specific reaction.