F17 UTA-711 Name Section Date PRELAB PROBLEMS EXPERIMENT UTA-711 1. Briefly defi
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F17 UTA-711 Name Section Date PRELAB PROBLEMS EXPERIMENT UTA-711 1. Briefly define shemiluminescence. How is it different from an exothermic reaction? 2. Write the molecular formula and determine the molar mass of luminol. 3. Briefly define a catalyst. 4. At minimum, what components are required to produce a chemiluminecent reaction in today's experiment? 5. Describe a sequence of test reactions that will allow you to systematically investigate the effects of concentration, pH, and added metal catalysts on the luminol reaction with hydrogen peroxide. (continue on the back of this page as needed)Explanation / Answer
1. Chemiluminescence is the production of light or photons through a chemical reaction. This is the reverse of a photochemical reaction in which light energy or photons are absorbed to drive a chemical reaction. Unlike explosive reactions, chemiluminescent reactions produce only light and not heat. This occurs due to the change in electronic state of the product in the reaction, which forms in its excited state and the light emission occurs when the electronically excited product relaxes back into its ground state.
This process is different from an exothermic reaction as instead of expulsion of heat from the system, the energy is released as light.
2. The molecular formula of Luminol is C8H7N3O2 and its molecular mass is 177.16g/mol.
3. A catalyst is any substance that alters the rate of the reaction by reversibly participating in the process and altering the energy required for the reactants to form the desired transition state, which decomposes to give the product, thereby accelerating both the forward and backward reactions equally.
4. For luminol to exhibit chemiluminescence, it should be treated with an oxidant. Usually the oxidant used is singlet dioxygen molecule produced conventionally by the reaction of hydrogen peroxide with a strong base with the latter serving as the activator for the chemiluminescent reaction.
5. Absence of precise experimental procedure prevents effectively answering this question as catalyst, solvent screening etc. are vital parameters for this answer.
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