The rate constant of the reaction between hydrochloric acid HCl and sodium thiosulfate Na2S2O3 can be determined experimentally. The reaction can be represented as:2HCl + Na2S2O3 2NaCl + H2O + SO2 + STo determine the rate constant k , you need to perform a series of experiments by varying the concentrations of HCl and Na2S2O3 and measuring the time taken for the reaction to complete. The rate law for this reaction can be expressed as:Rate = k [HCl]^m [Na2S2O3]^nwhere m and n are the orders of the reaction with respect to HCl and Na2S2O3, respectively.By performing experiments at different concentrations and measuring the time taken for the reaction to complete usually by monitoring the formation of the sulfur precipitate , you can determine the order of the reaction with respect to each reactant and the rate constant k .The rate constant value will depend on the specific experimental conditions, such as temperature and pressure. Therefore, it is not possible to provide a specific value for the rate constant without experimental data.