Changing the concentration of reactants in a chemical reaction, such as the reaction between sodium thiosulphate Na2S2O3 and hydrochloric acid HCl , can significantly affect the reaction rate and the yield of products. According to the collision theory, increasing the concentration of reactants increases the frequency of collisions between particles, which in turn increases the reaction rate.The reaction between sodium thiosulphate and hydrochloric acid can be represented by the following balanced equation:Na2S2O3 aq + 2 HCl aq 2 NaCl aq + SO2 g + S s + H2O l In this reaction, the yield of products sodium chloride, sulfur dioxide, sulfur, and water is directly proportional to the amount of reactants consumed. As the concentration of reactants increases, the reaction rate increases, leading to a faster formation of products.However, it is essential to note that increasing the concentration of reactants may not always result in a higher yield of products. This is because the reaction may reach a point where the rate of product formation becomes limited by other factors, such as the availability of reactants, temperature, or the presence of a catalyst.To determine the optimal concentration of reactants to achieve the highest yield, it is necessary to perform a series of experiments with varying concentrations of sodium thiosulphate and hydrochloric acid. By measuring the amount of product formed in each experiment, you can identify the concentration of reactants that results in the highest yield.In summary, changing the concentration of reactants in the reaction between sodium thiosulphate and hydrochloric acid affects the reaction rate and the yield of products. The optimal concentration of reactants to achieve the highest yield can be determined through experimentation.