The surface area of a reactant plays a significant role in the rate of a chemical reaction, including the reaction between hydrochloric acid HCl and magnesium Mg . The reaction between HCl and Mg can be represented by the following balanced chemical equation:Mg s + 2 HCl aq MgCl aq + H g When the surface area of a reactant, in this case, magnesium, is increased, the rate of reaction also increases. This is because a larger surface area allows for more particles of the reactant to be exposed and available for collisions with the other reactant, hydrochloric acid, at any given time. As a result, there is a higher probability of successful collisions between the reactant particles, leading to an increased rate of reaction.In practical terms, if you were to use a fine magnesium powder instead of a solid piece of magnesium, the reaction with hydrochloric acid would occur at a much faster rate. This is because the fine powder has a larger surface area compared to the solid piece, allowing for more collisions between the magnesium and hydrochloric acid particles.In summary, the surface area of a reactant, such as magnesium, has a direct impact on the rate of reaction with another reactant, like hydrochloric acid. An increased surface area leads to more successful collisions between reactant particles, resulting in a faster rate of reaction.