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Unformatted text preview: 1 Quantitative Chemical Analysis Seventh Edition Quantitative Chemical Analysis Seventh Edition Chapter 8 Systematic Treatment of Equilibrium Daniel C. Harris Daniel C. Harris Chapter Highlights Activity we just skip this part A systematic way to solve equilibrium problems: What are the equations? Charge balance? Material balance? Enough equations for variables? Solve! 2 Systematic Treatment of Equilibrium A way to deal with all types of chemical equilibria, regardless of their complexity. Write as many independent algebraic equations as there are unknowns (species) in the problem. The equations to be written: All the chemical equilibrium conditions The balances of charge The balances of mass Charge Balance The charge balance is an algebraic statement of electroneutrality: The sum of the positive charges in solution equals the sum of the negative charges in solution. Suppose that a solution contains the following ionic species: H + , OH , K + , H 2 PO 4 , HPO 4 2 , and PO 4 3 . The charge balance is: [H + ] + [K + ] = [OH ] +[H 2 PO 4 ] + 2[HPO 4 2 ] + 3[PO 4 3 ] The total charge contributed by H + and K + equals the magnitude of the charge contributed by all of the anions. The coefficient in front of each species always equals the magnitude of the charge on the ion. 3 Charge Balance Charge contributed by each ion in 1.00 L of solution containing 0.025 0 mol KH 2 PO 4 plus 0.0300 mol KOH. The total positive charge equals the total negative charge. Example Charge Balance In a certain equilibrium solution: Charge balance: 4 Charge Balance The general form of the charge balance for any solution is [C i ] is the concentration of a cation n i is the charge of the cation...
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 Fall '08
 BalintSztaray,Ph.D
 Analytical Chemistry, Equilibrium

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