The reaction between sodium thiosulfate Na2S2O3 and hydrochloric acid HCl can be represented by the following balanced equation:Na2S2O3 aq + 2 HCl aq 2 NaCl aq + SO2 g + S s + H2O l The effect of doubling the concentration of reactants on the reaction rate depends on the order of the reaction with respect to each reactant. For this reaction, it is generally considered to be a first-order reaction with respect to both sodium thiosulfate and hydrochloric acid.According to the rate law for a first-order reaction, the rate of the reaction is directly proportional to the concentration of the reactants. Therefore, if you double the concentration of both sodium thiosulfate and hydrochloric acid, the reaction rate will increase by a factor of 2 for each reactant.Since the reaction is first-order with respect to both reactants, the overall effect on the reaction rate will be a four-fold increase 2 x 2 = 4 . In other words, doubling the concentration of both sodium thiosulfate and hydrochloric acid will cause the reaction rate to increase by a factor of 4.