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Which factor would most significantly increase the rate of a reaction?

  1. Decreasing surface area

  2. Lowering temperature

  3. Increasing concentration of reactants

  4. Adding an inert gas

The correct answer is: Increasing concentration of reactants

Increasing the concentration of reactants significantly raises the rate of a reaction because it enhances the likelihood of effective collisions between the reactant molecules. In most chemical reactions, the rate is directly proportional to the concentration of the reactants. When the concentration is higher, there are more particles available in a given volume, which leads to a greater frequency of collisions. Since reactions occur when reactant particles collide with sufficient energy and the correct orientation, a higher concentration directly contributes to an increased number of such effective collisions. In contrast, decreasing surface area would limit the exposure of reactants to one another, effectively slowing down the reaction. Lowering the temperature reduces the kinetic energy of the molecules, which in turn decreases the rate of collisions and energy available to overcome activation energy, thus slowing the reaction. Adding an inert gas does not participate in the reaction, and while it may affect pressure dynamics in gaseous reactions, it does not influence the rate of the reaction itself involving reactants. Therefore, increasing concentration of reactants stands out as the most effective way to boost reaction rates among the choices provided.