The reaction rate of the reaction between sodium thiosulfate Na2S2O3 and hydrochloric acid HCl is affected by the concentration of the reactants. According to the collision theory, the rate of a reaction depends on the frequency of collisions between the reacting particles. When the concentration of reactants increases, the number of particles per unit volume also increases, leading to a higher probability of collisions between the particles.In the reaction between sodium thiosulfate and hydrochloric acid, the following reaction occurs:Na2S2O3 aq + 2 HCl aq 2 NaCl aq + SO2 g + S s + H2O l As the concentration of sodium thiosulfate and/or hydrochloric acid increases, the reaction rate will also increase due to the increased frequency of collisions between the reactant particles. This can be observed experimentally by measuring the time it takes for the reaction to produce a certain amount of sulfur S , which causes the solution to become cloudy.In summary, the concentration of reactants has a direct impact on the reaction rate of the reaction between sodium thiosulfate and hydrochloric acid. Higher concentrations of reactants lead to increased reaction rates due to the increased probability of collisions between the reacting particles.