Analytical Chem istry - DePauw University

270 Analytical Chemistry 2.0These redox reactions in this problem arenot balanced. You will need to balance thereactions before calculating their standardstate potentials. Although you may recallhow to do this from another course, thereis a much easier approach that you can usehere. Identify the oxidizing agent and thereducing agent and divide the reaction intotwo unbalanced half-reactions. Using Appendix13, find the appropriate balancedhalf-reactions. Add the two half-reactionstogether and simplify the stoichiometry toarrive at the balanced redox reaction.As an example, in (a) the oxidizing agent isMnO 4– and its unbalanced half-reactionisMnO− − 2+4( aq ) + 5e Mn ( aq )The corresponding balanced half-reactionfrom Appendix 13 isMnO− + −( aq ) + 8H( aq ) + 5e4Mn2+( aq ) + 4HO()lMost of the problems that follow require one ormore equilibrium constants or standard state potentials.For your convenience, here are hyperlinksto the appendices containing these constantsAppendix 10: Solubility ProductsAppendix 11: Acid Dissociation ConstantsAppendix 12: Metal-Ligand Formation ConstantsAppendix 13: Standard State Reduction Potentials24. Calculate the standard state potential and the equilibrium constant foreach of the following redox reactions. Assume that [H 3 O + ] is 1.0 M foracidic solutions, and that [OH – ] is 1.0 M for basic solutions.− 2+ 2−a. MnO ( aq) + H SO ( aq) Mn ( aq) + SO ( aq)acidicsolution4 2 34− −b. IO ( aq) + I ( aq) I () s acidic solution3 2c. ClO − ( aq) + I − ( aq) IO − ( ) + Cl −3aq ( aq)basicsolution5. One analytical method for determining the concentration of sulfur isto oxidize it to SO 4 2- and then precipitate it as BaSO 4 by adding BaCl 2 .The mass of the resulting precipitate is proportional to the amount ofsulfur in the original sample. The accuracy of this method depends onthe solubility of BaSO 4 , the reaction for which is shown here.22BaSO () s Ba + ( aq) + SO− ( aq )4How do the following affect the solubility of BaSO 4 and, therefore, theaccuracy of the analytical method?a. decreasing the solution’s pHb. adding more BaCl 2c. increasing the volume of the solution by adding H 2 O6. Write a charge balance equation and mass balance equations for the followingsolutions. Some solutions may have more than one mass balanceequation.a. 0.10 M NaClb. 0.10 M HClc. 0.10 M HFd. 0.10 M NaH 2 PO 4e. MgCO 3 (saturated solution)f. 0.10 M Ag(CN) 2–g. 0.10 M HCl and 0.050 M NaNO 247. Using the systematic approach to equilibrium problems, calculate thepH of the following solutions. Be sure to state and justify any assumptionsyou make in solving the problems.a. 0.050 M HClO 4b. 1.00 × 10 –7 M HClc. 0.025 M HClOd. 0.010 M HCOOHe. 0.050 M Ba(OH) 2f. 0.010 M C 5 H 5 N