The reaction between FeCl3 ferric chloride and KCNS potassium thiocyanate produces a complex ion, Fe SCN 3^2- ferric thiocyanate , which exhibits a deep red color. The reaction can be represented as follows:FeCl3 aq + 3 KCNS aq Fe SCN 3^2- aq + 3 KCl aq The reaction rate can affect the selectivity of this reaction in terms of the color change observed, as measured by UV-Vis spectroscopy, in several ways:1. Concentration of reactants: The reaction rate is directly proportional to the concentration of the reactants. If the concentration of either FeCl3 or KCNS is increased, the reaction rate will increase, leading to a faster formation of the Fe SCN 3^2- complex. This will result in a more rapid color change from colorless to deep red, which can be detected by UV-Vis spectroscopy.2. Temperature: The reaction rate is also affected by temperature. An increase in temperature generally leads to an increase in the reaction rate. This is because the kinetic energy of the molecules increases, resulting in more frequent and energetic collisions between the reactant molecules. Consequently, the formation of the Fe SCN 3^2- complex will be faster, leading to a quicker color change that can be monitored by UV-Vis spectroscopy.3. Presence of catalysts or inhibitors: The presence of a catalyst can increase the reaction rate by providing an alternative reaction pathway with a lower activation energy. This will lead to a faster formation of the Fe SCN 3^2- complex and a more rapid color change. Conversely, the presence of an inhibitor can decrease the reaction rate, resulting in a slower color change.In summary, the reaction rate can affect the selectivity of the reaction between FeCl3 and KCNS in terms of the color change observed, as measured by UV-Vis spectroscopy, by influencing the speed at which the Fe SCN 3^2- complex forms. Factors such as reactant concentration, temperature, and the presence of catalysts or inhibitors can all impact the reaction rate and, consequently, the observed color change.