March 2 - Absolute value of the charge. Ex. From section...

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March 2 If you mix very dilute acid (or base), the pH will approach 7.00 [neutral]. Acid Neutral Base ------dilute--------------- --------dilute------- Systematic Treatment of Equilibrium Identify all unique species in solution. Ex. Mix a weak acid, HA. Answer: HA [acid], A - [conj. Base]. All aqueous solutions have H + & OH - *If you have 4 unknowns, you need 4 equations to solve. 1. Kw = [H + ][OH - ] 2. Ka = [H + ][A - ] / [HA] 3. Material balance [Section 7.9]. 4. Charge balance Material Balance C HA [label /stated concentration] = [HA] + [A - ] Ex. For triprotic acid H 3 A C H3A [mixed concentration] = [H 3 A] + [H 2 A - ] +[HA 2- ] + [A 3- ] Charge Balance Σ all cations = Σ all anions [H + ] = [OH - ] + [A - ] Charge balance for a solution of FeCl 3 and Ca(NO 3 ) 2 .
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2[Ca 2+ ] + 3[Fe 3+ ] + [H + ] = [OH - ] + [Cl - ] + [NO 3 - ]
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Unformatted text preview: Absolute value of the charge. Ex. From section 7.10. Mix 1.0 x 10-8 M HCl. ?pH. Charge balance [H+] = [OH-] + [Cl-] Material balance 1.0 x 10-8 = [Cl-] Kw = [H+] [OH-] [OH-] = Kw / [H+] Equation: [H+] = Kw / [H+] + 1.0 x 10-8 X = Kw / X + 1.0 x 10-8 X 2 = Kw + 1.0 x 10-8 (x) X2 (10-8 )(x) Kw = 0 Quadratic Formula X = 1.05125 E-7-log (x) = 6.978 Polyprotic Acids Has more than one proton on it. Diprotic, Triprotic, Polyprotic. Triprotic: 1. H 3 A [Neutral] <-> H + + H 2 A- . K a1 2. H 2 A- <-> H + + HA 2-. K a2 3. HA 2- <-> H + + A 3-. K a3 Conjugates A 3-[base] + H 2 O <-> HA 2- + OH-K b1 HA 2- + H 2 O <-> H 2 A- + OH-K b2 H 2 A-+ H 2 O <-> H 3 A + OH-K b3 Ka * Kb = Kw Ka1 * Kb3 = Kw...
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March 2 - Absolute value of the charge. Ex. From section...

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