The effect of concentration on the reaction rate between magnesium and hydrochloric acid can be explained using the collision theory. According to this theory, the rate of a chemical reaction depends on the frequency of collisions between the reacting particles and the fraction of collisions that have enough energy to overcome the activation energy barrier.When the concentration of hydrochloric acid is increased, there are more acid particles present in the solution. This leads to a higher probability of collisions between the magnesium and acid particles, resulting in an increased reaction rate. Conversely, when the concentration of hydrochloric acid is decreased, there are fewer acid particles, leading to a lower reaction rate.To increase the sustainability of the reaction, one can optimize the concentration of hydrochloric acid to achieve the desired reaction rate while minimizing the consumption of resources and the production of waste. This can be done by conducting experiments to determine the optimal concentration that provides the required reaction rate without using an excessive amount of hydrochloric acid.Additionally, recycling and reusing the byproducts of the reaction can also contribute to the sustainability of the process. For example, the reaction between magnesium and hydrochloric acid produces magnesium chloride and hydrogen gas:Mg s + 2HCl aq MgCl2 aq + H2 g Magnesium chloride can be used in various applications, such as de-icing agents, dust suppressants, and as a source of magnesium in the production of other compounds. Hydrogen gas can be used as a clean fuel or in the production of other chemicals. By finding ways to utilize these byproducts, the overall sustainability of the reaction can be improved.