Changing the concentration of the reactants in a chemical reaction can significantly affect the rate of reaction and the sustainability of the reaction. 1. Rate of Reaction: According to the collision theory, the rate of a chemical reaction depends on the frequency of collisions between the reactant molecules. When the concentration of reactants is increased, there are more reactant molecules in the same volume, leading to a higher probability of collisions between them. As a result, the rate of reaction increases. Conversely, when the concentration of reactants is decreased, the rate of reaction decreases due to fewer collisions between the reactant molecules.2. Sustainability of the Reaction: The sustainability of a reaction refers to the ability of the reaction to continue until the reactants are completely consumed or until equilibrium is reached. Changing the concentration of reactants can affect the sustainability of the reaction in the following ways:a. If the concentration of reactants is too high, the reaction may proceed too quickly, generating a large amount of heat and potentially causing the reaction to become uncontrollable or hazardous. In some cases, this could lead to a runaway reaction or an explosion.b. If the concentration of reactants is too low, the reaction may not proceed efficiently, and the desired products may not be formed in sufficient quantities. This could lead to a waste of resources and energy, making the reaction less sustainable.c. In reversible reactions, changing the concentration of reactants can shift the position of the equilibrium, affecting the sustainability of the reaction. According to Le Chatelier's principle, if the concentration of reactants is increased, the equilibrium will shift towards the products, making the reaction more sustainable. On the other hand, if the concentration of reactants is decreased, the equilibrium will shift towards the reactants, making the reaction less sustainable.In conclusion, changing the concentration of reactants can have a significant impact on both the rate of reaction and the sustainability of the reaction. To optimize a chemical reaction, it is essential to carefully control the concentration of reactants to achieve the desired reaction rate while maintaining the sustainability of the reaction.