The reaction between magnesium Mg and hydrochloric acid HCl can be represented by the following balanced chemical equation:Mg s + 2HCl aq MgCl2 aq + H2 g The effect of initial concentration on the reaction rate and yield can be explained using the collision theory and Le Chatelier's principle.1. Reaction rate: According to the collision theory, the rate of a reaction depends on the frequency of effective collisions between the reactant particles. When the initial concentration of hydrochloric acid is increased, there will be more HCl molecules available to collide with magnesium atoms. This results in a higher frequency of effective collisions, leading to an increased reaction rate. Conversely, if the initial concentration of HCl is decreased, the reaction rate will be slower due to fewer effective collisions.2. Reaction yield: In the case of the reaction between magnesium and hydrochloric acid, the reaction goes to completion, meaning that all of the magnesium reacts with the hydrochloric acid to form magnesium chloride and hydrogen gas. Therefore, the yield of the reaction is not directly affected by the initial concentration of HCl. However, if there is an excess of HCl, the reaction will still go to completion, but there will be leftover unreacted HCl. On the other hand, if there is not enough HCl to react with all of the magnesium, the reaction will stop when all of the HCl has been consumed, resulting in a lower yield of magnesium chloride and hydrogen gas.In summary, increasing the initial concentration of hydrochloric acid in the reaction with magnesium will increase the reaction rate, but the reaction yield will not be directly affected as long as there is enough HCl to react with all of the magnesium.