The reaction between hydrochloric acid HCl and magnesium Mg can be represented by the following balanced chemical equation:Mg s + 2HCl 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 the concentration of hydrochloric acid, which is directly related to the pH of the solution. pH is a measure of the acidity or alkalinity of a solution, with lower pH values indicating higher acidity and higher pH values indicating lower acidity.As the pH of the hydrochloric acid solution decreases i.e., the acidity increases , the concentration of HCl increases. This leads to an increase in the reaction rate between HCl and Mg, as there are more HCl molecules available to react with the magnesium. The reaction will proceed more quickly, producing magnesium chloride and hydrogen gas at a faster rate.Conversely, as the pH of the hydrochloric acid solution increases i.e., the acidity decreases , the concentration of HCl decreases. This leads to a decrease in the reaction rate between HCl and Mg, as there are fewer HCl molecules available to react with the magnesium. The reaction will proceed more slowly, producing magnesium chloride and hydrogen gas at a slower rate.In summary, changes in pH have a direct effect on the reaction rate between hydrochloric acid and magnesium. Lower pH values higher acidity result in faster reaction rates, while higher pH values lower acidity result in slower reaction rates.