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 As the pH of the solution varies from 1 to 7, the concentration of HCl in the solution decreases. The pH is a measure of the acidity of a solution, with lower pH values indicating higher acidity and higher HCl concentration. The pH scale is logarithmic, meaning that a change of 1 pH unit corresponds to a tenfold change in the concentration of H+ ions which are produced by HCl in solution .The reaction rate of this reaction is directly proportional to the concentration of HCl in the solution. As the pH increases from 1 to 7, the concentration of HCl decreases, leading to a decrease in the reaction rate. This is because there are fewer HCl molecules available to react with the magnesium, resulting in a slower rate of reaction.In summary, as the pH of the solution increases from 1 to 7, the reaction rate measured in moles per second of the reaction between hydrochloric acid HCl and magnesium Mg decreases.