Question

Kinetics of the Oxidation of a Water Soluable Dye: Explain the following three factors - (1) Discuss the kinetics of the oxidation reaction of blue dye (used as a food coloring) by common household bleach, (2) talk abouthow to determine the reaction order of this oxidation with respect to bleach and dye, and lastly, (3) talk about the quantitative and qualitative measures of how changes in temperature affect the reaction rate (provide a graphical illustration relating the significance of the integrated rate laws. Thanks!

Answer 1

1) Because of the extended conjugation of alternating double bonds within the molecule, the absorption occurs in the visible region of the spectrum at 628 nm. When the dye reacts with hypochlorite, the colour disappears. One possible explanation for this reaction is that the bleach oxidises the central methylene carbon atom so that the molecule no longer has the extend conjugation system and the absorption of the less conjugated product occurs at a lower wavelength outside of the visible region of the spectrum. The product might be an alcohol compound depicted in the reaction below. A study of how the concentration of the reactants affect the rate of the reaction gives insight into the mechanism and whether this simple explanation might be correct.The rate of a reaction can be represented either by the disappearance of reactants or the appearance of products. Since Blue dye is the only coloured species in the reaction, we can monitor the rate of the reaction shown above by recording the decrease in the colour of solution with time.

2) We also present the rate law for the reaction

Dye + ClO^- products

despite not having knowledge of the stoichiometry nor the products of the reaction. The general form of the rate law for the reaction can be written:

Rate = k

Since x and y are not directly related to the stoichiometry of the reaction the correct reaction stoichiometry doesn’t need to be known. The values of x and y are the orders of the reaction in the respective reactant and k is the rate constant for the reaction. The reaction orders can be obtained by the method of initial rates or by linearizing the concentration vs. time plot with the integrated rate law of the appropriate order (zeroeth, first, or second order).

3) Temperature is considered a major factor that affects the rate of a chemical reaction. It is considered a source of energy in order to have a chemical reaction occur. Svante Arrhenius, a Swedish chemist, believed that the reactants in a chemical reaction needed to gain a small amount of energy in order to become products. He called this type of energy the activation energy. The amount of energy used in the reaction is known to be greater than the activation energy in the reaction. food coloring is added to cold water, room temperature water, and hot water. When the substance mixes with the hot water, the high temperatures allow it become a homogeneous mixture. This is because due to water molecules moving faster when the temperature is higher and speeding up the dissolution reaction.