Sounds easy doesnt it there is one more catch in order

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Unformatted text preview: monitoring the absorbance at 260 nm will be unproductive since we will not be able to distinguish between NAD+ and NADH at this wavelength. However, the reduced pyridinium of NADH absorbs 340 nm light whereas NAD+ does not absorb light at this wavelength. We can therefore follow the reaction by monitoring the absorption at 340 nm – at this wavelength, any absorbance will be due to the presence of NADH. When the absorption at that wavelength peaks and remains constant, the reaction has reached equilibrium. We can then use Beer’s Law to determine the concentration of the NADH. Once we have this, we can determine the equilibrium constant. Sounds easy, doesn’t it? There is one more catch: in order to use Beer’s Law to determine the concentration of NADH, we will need to determine the molar absorptivity. Luckily, we already know how to do that, right? We’ll make a standard curve by using known concentrations of NADH and plotting the absorbance vs. concentration. Once we do that, obtaining the molar absorptivity is simple! Possible Quiz Questions 1. Given that the reaction studied in this experiment is: CH 3CH 2OH + NAD+ "ADH→ CH 3CHO + NADH + H + " " 2. 3. 4. 5. 6. 7. 8. Determine the equilibrium constant if the initial concentration of ethanol was 2.25 x 10- 2 M, the initial concentration of NAD+ was 1.45 x 10- 4 M, the absorbance of NADH at equilibrium is 0.335 and the molar absorptivity of NADH is 6220 M- 1 cm- 1. € Determine the molar absorptivity of 1, 10- phenanthroline given the following data (you m...
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This lab report was uploaded on 04/06/2014 for the course CHEM 272 taught by Professor Dr.brooks during the Summer '08 term at Maryland.

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