Changing the concentration of reactants in a chemical reaction can significantly impact the reaction rate and sustainability of the reaction. 1. Reaction rate: According to the collision theory, the reaction rate is directly proportional to the frequency of effective collisions between reactant molecules. When the concentration of reactants is increased, the number of reactant molecules per unit volume also increases. This leads to a higher probability of collisions between reactant molecules, resulting in an increased reaction rate. Conversely, when the concentration of reactants is decreased, the reaction rate decreases due to fewer collisions between reactant molecules.2. Sustainability: The sustainability of a chemical reaction refers to its ability to continue over time without depleting the reactants or causing adverse effects on the environment. Changing the concentration of reactants can affect the sustainability of a reaction in several ways:a If the concentration of reactants is too high, the reaction may proceed too quickly, leading to a rapid depletion of reactants and a shorter reaction duration. This can also result in the production of unwanted by-products or side reactions, which can negatively impact the environment.b If the concentration of reactants is too low, the reaction may proceed too slowly or not at all, making it unsustainable. In this case, increasing the concentration of reactants may be necessary to achieve a sustainable reaction rate.c In some cases, the optimal concentration of reactants for sustainability may be a balance between the reaction rate and the environmental impact. For example, a reaction that produces harmful by-products may be more sustainable at a lower concentration, even if the reaction rate is slower, because it minimizes the production of these by-products.In conclusion, changing the concentration of reactants can significantly affect the reaction rate and sustainability of a chemical reaction. It is essential to consider these factors when designing and optimizing chemical processes to ensure that they are both efficient and environmentally friendly.