The effect of pH on the rate of reaction between hydrochloric acid HCl and magnesium ribbon Mg can be understood by considering the fact that pH is a measure of the concentration of hydrogen ions H+ in a solution. In this reaction, the hydrochloric acid acts as a source of H+ ions, which react with the magnesium to form magnesium chloride MgCl2 and hydrogen gas H2 .Mg s + 2HCl aq MgCl2 aq + H2 g As the pH of the hydrochloric acid solution decreases i.e., becomes more acidic , the concentration of H+ ions increases. This higher concentration of H+ ions leads to a faster rate of reaction between the hydrochloric acid and magnesium ribbon. Conversely, as the pH of the hydrochloric acid solution increases i.e., becomes less acidic or more basic , the concentration of H+ ions decreases, resulting in a slower rate of reaction.In summary, the rate of reaction between hydrochloric acid and magnesium ribbon is directly proportional to the concentration of H+ ions in the solution, which is inversely proportional to the pH value. Therefore, a lower pH more acidic solution will result in a faster rate of reaction, while a higher pH less acidic or more basic solution will result in a slower rate of reaction.