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  <head>
    <title>105-02 Acid–base equilibria, buffers, and titration reasoning</title>
    <ownerName>Integrated Medical Foundations</ownerName>
  </head>
  <body>
    <outline text="Acid–base equilibria, buffers, titration">
      <outline text="Framing the problem">
        <outline text="Identify proton donor, acceptor, conserved quantities"/>
        <outline text="Near-complete reaction or reversible equilibrium">
          <outline text="Confusing the stages wrecks buffer calculations"/>
        </outline>
        <outline text="Ideal dilute aqueous solutions at 25 °C"/>
      </outline>
      <outline text="Acid and base definitions">
        <outline text="Brønsted–Lowry: acid donates, base accepts proton"/>
        <outline text="Conjugate pair differs by one proton and one charge"/>
        <outline text="Lewis: acid accepts, base donates electron pair">
          <outline text="Proton transfer fits within Lewis view"/>
          <outline text="Lewis interaction need not transfer a proton"/>
        </outline>
        <outline text="State which definition is in use"/>
      </outline>
      <outline text="Logarithmic measurement">
        <outline text="pH: negative log of hydrogen-ion activity">
          <outline text="Dilute problems approximate activity by concentration"/>
        </outline>
        <outline text="One pH unit is a tenfold activity change">
          <outline text="Two units is a hundredfold ratio"/>
          <outline text="Averaging pH values misdescribes mixtures"/>
        </outline>
        <outline text="Water&#x27;s ion product about 10^-14 at 25 °C">
          <outline text="pH plus pOH about 14"/>
        </outline>
        <outline text="Neutral means equal H+ and OH- activities">
          <outline text="Neutral pH shifts with the ion product"/>
        </outline>
        <outline text="0 to 14 is not an absolute boundary"/>
      </outline>
      <outline text="Strength versus concentration">
        <outline text="Ka compares product activities with acid activity">
          <outline text="Larger Ka, smaller pKa: stronger acid"/>
        </outline>
        <outline text="Concentration is acid supplied per volume"/>
        <outline text="Dilute strong vs concentrated weak: words cannot rank"/>
        <outline text="Worked weak acid: 0.040 M, Ka 10^-5">
          <outline text="Small-change approximation gives pH about 3.20"/>
          <outline text="Only about 1.58% dissociates"/>
          <outline text="Exact quadratic gives nearly the same pH"/>
        </outline>
        <outline text="Check assumptions after calculating">
          <outline text="Large dissociation: keep depleted acid term"/>
          <outline text="10^-8 M strong acid does not give pH 8"/>
          <outline text="Water equilibrium puts pH slightly below 7"/>
        </outline>
      </outline>
      <outline text="Buffers as finite reserves">
        <outline text="Weak acid with conjugate base, or weak-base pair"/>
        <outline text="Added acid consumes base component, and vice versa">
          <outline text="pH changes less than unbuffered solution"/>
        </outline>
        <outline text="Henderson–Hasselbalch: pH = pKa + log(base/acid)">
          <outline text="Neither component may be zero"/>
        </outline>
        <outline text="Equal 10.0 mmol pair at pKa 5 gives pH 5">
          <outline text="2.00 mmol strong acid converts A- to HA"/>
          <outline text="Post-reaction ratio 8:12 gives pH 4.82"/>
          <outline text="Initial ratio wrongly predicts no change"/>
        </outline>
      </outline>
      <outline text="Buffer capacity">
        <outline text="Same pH with only 1.00 mmol each">
          <outline text="Base exhausted, excess strong acid remains"/>
          <outline text="No longer a two-component buffer"/>
        </outline>
        <outline text="Capacity depends on amount, not pH alone"/>
        <outline text="Dilution keeps ratio and roughly pH">
          <outline text="Fixed volume then holds less capacity"/>
        </outline>
      </outline>
      <outline text="Titration regions">
        <outline text="Equivalence point: stoichiometric amounts reacted"/>
        <outline text="Endpoint: indicator or instrument signal">
          <outline text="Close in a good method, not the same event"/>
        </outline>
        <outline text="Before equivalence: acid and conjugate base coexist"/>
        <outline text="Half-equivalence: pH approximates pKa"/>
        <outline text="Example: 2.00 mmol weak acid, 0.100 M base">
          <outline text="Equivalence at 20.0 mL, half at 10.0 mL"/>
        </outline>
        <outline text="Beyond equivalence, excess strong base dominates">
          <outline text="25.0 mL leaves 0.50 mmol in 50.0 mL"/>
          <outline text="OH- 0.0100 M, pH 12"/>
        </outline>
        <outline text="Each region needs a different model"/>
      </outline>
      <outline text="Equivalence-point pH">
        <outline text="Conjugate base reacts with water">
          <outline text="Weak acid, strong base: pH above 7"/>
          <outline text="Strong acid, strong base: neutral, no hydrolysis"/>
        </outline>
        <outline text="Ka times Kb equals water ion product">
          <outline text="Ka 10^-5 gives Kb 10^-9"/>
        </outline>
        <outline text="2.00 mmol in 45.0 mL is about 0.0444 M"/>
        <outline text="OH- about square root of Kb times concentration">
          <outline text="pOH about 5.18, pH about 8.82"/>
        </outline>
      </outline>
      <outline text="Mixing strong acids">
        <outline text="Equal volumes at pH 2 and pH 4">
          <outline text="H+ about 0.00505 M, pH about 2.30, not 3"/>
          <outline text="Concentrated solution supplies most H+"/>
        </outline>
        <outline text="Assumes additive volumes, negligible water"/>
      </outline>
      <outline text="Protonation in biology">
        <outline text="One unit above pKa: about 10 deprotonated per 1"/>
        <outline text="One unit below: the reverse ratio"/>
        <outline text="Proteins have multiple interacting groups">
          <outline text="One group cannot fix whole-protein charge"/>
        </outline>
        <outline text="Polyprotic acids lose protons stepwise"/>
        <outline text="Solving habit">
          <outline text="Identify species, finish dominant stoichiometry"/>
          <outline text="Choose equilibrium model"/>
          <outline text="Test charge balance and direction of change"/>
        </outline>
      </outline>
    </outline>
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