The reaction between hydrochloric acid HCl and magnesium Mg is an acid-base reaction that can be represented by the following balanced chemical equation:Mg s + 2 HCl aq MgCl2 aq + H2 g When the concentration of reactants is varied, it affects the reaction rate and the sustainability of the reaction.1. Reaction rate: According to the collision theory, the reaction rate depends on the frequency of effective collisions between the reacting particles. As the concentration of reactants increases, the number of particles per unit volume also increases. This leads to a higher probability of effective collisions between the reactant particles, resulting in an increased reaction rate. In the case of the reaction between hydrochloric acid and magnesium, increasing the concentration of hydrochloric acid will increase the reaction rate, leading to faster production of magnesium chloride and hydrogen gas.2. Sustainability of the reaction: The sustainability of a reaction refers to the ability of the reaction to continue until one of the reactants is completely consumed. In the case of the reaction between hydrochloric acid and magnesium, the sustainability of the reaction depends on the availability of both reactants. If the concentration of one reactant is significantly higher than the other, the reaction will continue until the limiting reactant is completely consumed, and the reaction will stop. For a more sustainable reaction, it is essential to maintain an appropriate ratio of the reactant concentrations.In summary, varying the concentration of reactants in the chemical reaction between hydrochloric acid and magnesium affects the reaction rate and the sustainability of the reaction. Increasing the concentration of reactants generally leads to a faster reaction rate, while maintaining an appropriate ratio of reactant concentrations ensures a more sustainable reaction.