The concentration of reactants plays a crucial role in determining the rate of a chemical reaction and its sustainability over a period of time. According to the collision theory, a reaction occurs when reactant particles collide with each other with sufficient energy and proper orientation. The rate of a reaction depends on the frequency and effectiveness of these collisions. Here's how the concentration of reactants affects the rate of the reaction and its sustainability:1. Increased concentration of reactants: When the concentration of reactants is increased, there are more particles present in a given volume. This leads to a higher frequency of collisions between reactant particles, resulting in an increased reaction rate. However, as the reaction proceeds, the concentration of reactants decreases, and the reaction rate slows down. The reaction will continue until the reactants are completely consumed or reach equilibrium with the products.2. Decreased concentration of reactants: When the concentration of reactants is decreased, there are fewer particles present in a given volume. This leads to a lower frequency of collisions between reactant particles, resulting in a decreased reaction rate. The reaction will also take a longer time to reach completion or equilibrium, making it less sustainable over a period of time.3. Sustainability: The sustainability of a reaction over a period of time depends on the availability of reactants and the rate at which they are consumed. If the concentration of reactants is high, the reaction can proceed at a faster rate and be sustained for a longer time. However, if the concentration of reactants is low, the reaction will be slower and may not be sustainable over a long period.In summary, the concentration of reactants directly affects the rate of a chemical reaction and its sustainability over time. Higher concentrations lead to faster reaction rates and increased sustainability, while lower concentrations result in slower reaction rates and decreased sustainability.