The reaction between hydrochloric acid HCl and magnesium Mg can be represented by the following balanced chemical equation:Mg s + 2 HCl aq MgCl2 aq + H2 g In this reaction, magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas. The reaction rate is influenced by several factors, including the concentration of hydrochloric acid.According to the collision theory, the rate of a chemical reaction depends on the frequency of collisions between reactant particles and the fraction of collisions that have sufficient energy to overcome the activation energy barrier. As the concentration of hydrochloric acid increases, the number of HCl molecules in the solution also increases. This leads to a higher frequency of collisions between HCl molecules and magnesium atoms, which in turn increases the reaction rate.In other words, when the concentration of hydrochloric acid is increased, the reaction between HCl and Mg occurs more rapidly, and the production of hydrogen gas is faster. This is because there are more HCl molecules available to react with the magnesium atoms, leading to a higher probability of successful collisions and a faster reaction rate.However, it is important to note that increasing the concentration of hydrochloric acid will not affect the overall efficiency of the reaction, as the stoichiometry of the reaction remains the same. The efficiency of the reaction refers to the ratio of the actual yield of products to the theoretical yield, which is determined by the balanced chemical equation. In this case, the efficiency of the reaction will remain constant, as long as other factors, such as temperature and pressure, are kept constant.In summary, increasing the concentration of hydrochloric acid in the reaction between HCl and magnesium will result in a faster reaction rate and a quicker production of hydrogen gas, but it will not affect the overall efficiency of the reaction.