Which method for chlorine dioxide generation is most likely to have substantial amounts of chlorine in solution?

The method that involves adding chlorine to water, then to hydrochloric acid and sodium chlorate is known for producing substantial amounts of chlorine in solution. This reaction occurs as chlorine is introduced as a reactant, and the presence of hydrochloric acid facilitates its interaction with sodium chlorate. This process leads to the generation of chlorine dioxide but also produces free chlorine as a byproduct because the reaction can favor the formation of free chlorine, especially when strong acids like hydrochloric acid are present.

This method utilizes the oxidative potential of chlorine, and because both chlorine and chlorate ions are present in the reaction, it results in a mix of both chlorine and chlorine dioxide. Therefore, it distinguishes itself from other methods of chlorine dioxide generation that either do not involve chlorine or do not rely on such a combination of reactants.

Other methods, like mixing sodium chlorate with ozone or electrolyzing water, typically do not introduce chlorine into the system, instead focusing on generating chlorine dioxide directly or using processes where chlorine is not a product. Direct injection of chlorine dioxide does not involve the generation of chlorine in the solution; rather, it directly adds chlorine dioxide. Hence, option B stands out as it inherently involves the generation of chlorine along with chlorine dioxide due to the chemical reactions taking