Changes in reactant concentration can significantly affect the rate of a chemical reaction and its sustainability. The relationship between reactant concentration and reaction rate is described by the rate law, which is determined experimentally for each specific reaction.1. Increased reactant concentration: When the concentration of one or more reactants is increased, the reaction rate generally increases. This is because there are more reactant particles available to collide with each other, leading to a higher probability of successful collisions and formation of products. This can be beneficial in industrial processes where a faster reaction rate is desired.2. Decreased reactant concentration: Conversely, when the concentration of one or more reactants is decreased, the reaction rate generally decreases. This is due to fewer reactant particles being available for collisions, resulting in a lower probability of successful collisions and product formation. In some cases, this can be advantageous, such as when controlling the rate of a reaction to prevent it from becoming too vigorous or dangerous.3. Sustainability: The sustainability of a chemical reaction depends on the availability and renewability of the reactants. If the reactants are non-renewable or scarce, increasing their concentration to achieve a faster reaction rate may not be sustainable in the long term. On the other hand, if the reactants are renewable or abundant, increasing their concentration may be more sustainable.4. Equilibrium: In reversible reactions, changes in reactant concentration can also affect the position of the equilibrium. According to Le Chatelier's principle, if the concentration of a reactant is increased, the equilibrium will shift in the direction that consumes the added reactant, leading to the formation of more products. Conversely, if the concentration of a reactant is decreased, the equilibrium will shift in the direction that produces more of the removed reactant, leading to the formation of fewer products.In summary, changes in reactant concentration can significantly affect the rate of a chemical reaction and its sustainability. Increasing reactant concentration generally leads to a faster reaction rate, while decreasing it results in a slower rate. The sustainability of a reaction depends on the availability and renewability of the reactants, and the position of the equilibrium can also be affected by changes in reactant concentration.