The rate of reaction between hydrochloric acid HCl and magnesium ribbon Mg can be affected by changing the pH of the solution. The reaction between HCl and Mg is as follows:Mg s + 2HCl aq MgCl2 aq + H2 g When the pH of the solution is changed, it means that the concentration of HCl is being altered. A lower pH indicates a higher concentration of HCl, while a higher pH indicates a lower concentration of HCl.In general, increasing the concentration of a reactant in a chemical reaction will increase the rate of the reaction, as there are more reactant particles available to collide and react with each other. Therefore, decreasing the pH increasing the concentration of HCl will increase the rate of reaction between HCl and Mg. Conversely, increasing the pH decreasing the concentration of HCl will decrease the rate of reaction.It is important to note that the relationship between pH and reaction rate may not be linear, and other factors such as temperature, pressure, and the presence of catalysts can also affect the rate of reaction.