CHEM3635 Practice Questions 1. Given the half equations and corresponding electrode potentials given in Table 1 below. i) Write an equation for the reaction that will most likely spontaneously take place between the two species and calculate E’ of the cell. [4 marks] ii) Hence, calculate G’ and K for the reaction. [8 marks] Table 1: Standard reduction Potential for Some Biological Half Reactions at 25C (pH=7) System NAD+ / NADH FMN / FMNH2 Half-Cell Reaction + 2H+ + 2e- NADH + H+ FMN + 2H+ + 2e- FMNH2 NAD+ E’ (V) -0.320 -0.219 2. Calculate the biological standard potential of the following half reaction at 25°C, given its value of +1.23V under thermodynamic standard conditions. O2 (g) 4H 4e 2H2O(l) 3. The oxidation of malate to oxaloacetate is a key reaction in the Krebs cycle. Using the information in table 1 below, i. Write an equation for the reaction ii. Hence, calculate G° and iii. Calculate the equilibrium constant for the reaction. Table 1 Standard Reduction Potential for Some Biological Half Reactions at 298K (pH 7) System Half-Cell Reaction Oxaloacetate / malate -OOC–COCH COO2 NAD+ / NADH NAD+ + 2H+ + 2e- NADH + H+ [10 marks] + 2H+ + 2e- -OOCCHOHCH2COO- E° (V) -0.166 -0.320 4. When Fe is complexed with H2O, the Fe3+/Fe2+ redox potential is +0.771 V. State with reason whether a lower or higher redox potential is expected when Fe is complexed with a) CO b) O2- 5. The E for the reaction NAD H 2e NADH is -0.320V at 25°C. Calculate the value at pH = 1. Assume that both NAD+ and NADH are in unimolar concentrations.