The reaction between sodium thiosulphate Na2S2O3 and hydrochloric acid HCl is a well-known reaction in chemistry, often used to study reaction rates. The reaction produces a precipitate of sulfur S , which causes the solution to become cloudy. The reaction can be represented by the following equation:Na2S2O3 aq + 2HCl aq 2NaCl aq + S s + SO2 g + H2O l The intensity of light does not directly affect the rate of the reaction between sodium thiosulphate and hydrochloric acid. This reaction is not a photochemical reaction, meaning it is not driven or influenced by light energy. Instead, the reaction rate is primarily influenced by factors such as concentration, temperature, and the presence of catalysts.However, the intensity of light can be used as an indirect method to measure the reaction rate. By shining a light through the reaction mixture and measuring the time it takes for the solution to become cloudy enough to obscure the light, one can determine the reaction rate. This method is known as the "disappearing cross" experiment, as a cross or other shape is often placed beneath the reaction vessel, and the time it takes for the cross to no longer be visible is recorded.In summary, while the intensity of light does not directly affect the rate of the reaction between sodium thiosulphate and hydrochloric acid, it can be used as a tool to measure the reaction rate. The primary factors affecting the reaction rate are concentration, temperature, and the presence of catalysts.