Percent Dissociated from Titration Curve












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Question 818 references the titration curve. Answer is A because $ce{H+}$ conc $= 10^{-4}$. This is conc of dissociated acid. The conc of the undissociated acid is the original concentration minus this: $0.1 - 0.0001$, which is about $0.1$. So then its $frac{0.0001}{0.1}times 100 = 0.1%$.



Where in the world are they getting the original concentration? how did they get $0.1$ as the concentration of undissociated acid?










share|improve this question











$endgroup$

















    2












    $begingroup$


    enter image description here



    Question 818 references the titration curve. Answer is A because $ce{H+}$ conc $= 10^{-4}$. This is conc of dissociated acid. The conc of the undissociated acid is the original concentration minus this: $0.1 - 0.0001$, which is about $0.1$. So then its $frac{0.0001}{0.1}times 100 = 0.1%$.



    Where in the world are they getting the original concentration? how did they get $0.1$ as the concentration of undissociated acid?










    share|improve this question











    $endgroup$















      2












      2








      2





      $begingroup$


      enter image description here



      Question 818 references the titration curve. Answer is A because $ce{H+}$ conc $= 10^{-4}$. This is conc of dissociated acid. The conc of the undissociated acid is the original concentration minus this: $0.1 - 0.0001$, which is about $0.1$. So then its $frac{0.0001}{0.1}times 100 = 0.1%$.



      Where in the world are they getting the original concentration? how did they get $0.1$ as the concentration of undissociated acid?










      share|improve this question











      $endgroup$




      enter image description here



      Question 818 references the titration curve. Answer is A because $ce{H+}$ conc $= 10^{-4}$. This is conc of dissociated acid. The conc of the undissociated acid is the original concentration minus this: $0.1 - 0.0001$, which is about $0.1$. So then its $frac{0.0001}{0.1}times 100 = 0.1%$.



      Where in the world are they getting the original concentration? how did they get $0.1$ as the concentration of undissociated acid?







      acid-base aqueous-solution analytical-chemistry titration






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      edited Apr 1 at 17:10









      Mathew Mahindaratne

      6,022725




      6,022725










      asked Apr 1 at 14:31









      JonJon

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      232






















          1 Answer
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          $begingroup$

          I'm not sure I follow your logic.
          For a monobasic acid S $(ce{HA})$ dissociation degree $α$ is



          $$α = frac{[ce{H+}]}{c_mathrm{a}},$$



          where $c_mathrm{a}$ is the initial concentration of the acid which you are determining via titration with the defined volume of a strong base $V_mathrm{b}$:



          $$c_mathrm{a}V_mathrm{a} = c_mathrm{b}V_mathrm{b} implies c_mathrm{a} = frac{c_mathrm{b}V_mathrm{b}}{V_mathrm{a}}$$



          Finally, taking $V_mathrm{a} = V_mathrm{b} = pu{50 mL}$ (from the figure's caption and equilibrium point) and, as you already assumed from pH, $[ce{H+}] approx pu{1e-4 mol L-1}$:



          $$α = frac{[ce{H+}]V_mathrm{a}}{c_mathrm{b}V_mathrm{b}} = frac{pu{1e-4 mol L-1}cdotpu{50 mL}}{pu{0.1 mol L-1}cdotpu{50 mL}} = pu{1e-3}~text{or}~0.1%$$






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thank you! I appreciate your help. I seem to have missed the entire purpose of the titration... so the idea is that you are setting the molar amount of base to the molar amount of acid specifically at the equivalence point, then solving for the original concentration of acid. then you divide the hydrogen ion concentration by this value
            $endgroup$
            – Jon
            Apr 1 at 15:00














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          1 Answer
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          1 Answer
          1






          active

          oldest

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          active

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          active

          oldest

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          6












          $begingroup$

          I'm not sure I follow your logic.
          For a monobasic acid S $(ce{HA})$ dissociation degree $α$ is



          $$α = frac{[ce{H+}]}{c_mathrm{a}},$$



          where $c_mathrm{a}$ is the initial concentration of the acid which you are determining via titration with the defined volume of a strong base $V_mathrm{b}$:



          $$c_mathrm{a}V_mathrm{a} = c_mathrm{b}V_mathrm{b} implies c_mathrm{a} = frac{c_mathrm{b}V_mathrm{b}}{V_mathrm{a}}$$



          Finally, taking $V_mathrm{a} = V_mathrm{b} = pu{50 mL}$ (from the figure's caption and equilibrium point) and, as you already assumed from pH, $[ce{H+}] approx pu{1e-4 mol L-1}$:



          $$α = frac{[ce{H+}]V_mathrm{a}}{c_mathrm{b}V_mathrm{b}} = frac{pu{1e-4 mol L-1}cdotpu{50 mL}}{pu{0.1 mol L-1}cdotpu{50 mL}} = pu{1e-3}~text{or}~0.1%$$






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thank you! I appreciate your help. I seem to have missed the entire purpose of the titration... so the idea is that you are setting the molar amount of base to the molar amount of acid specifically at the equivalence point, then solving for the original concentration of acid. then you divide the hydrogen ion concentration by this value
            $endgroup$
            – Jon
            Apr 1 at 15:00


















          6












          $begingroup$

          I'm not sure I follow your logic.
          For a monobasic acid S $(ce{HA})$ dissociation degree $α$ is



          $$α = frac{[ce{H+}]}{c_mathrm{a}},$$



          where $c_mathrm{a}$ is the initial concentration of the acid which you are determining via titration with the defined volume of a strong base $V_mathrm{b}$:



          $$c_mathrm{a}V_mathrm{a} = c_mathrm{b}V_mathrm{b} implies c_mathrm{a} = frac{c_mathrm{b}V_mathrm{b}}{V_mathrm{a}}$$



          Finally, taking $V_mathrm{a} = V_mathrm{b} = pu{50 mL}$ (from the figure's caption and equilibrium point) and, as you already assumed from pH, $[ce{H+}] approx pu{1e-4 mol L-1}$:



          $$α = frac{[ce{H+}]V_mathrm{a}}{c_mathrm{b}V_mathrm{b}} = frac{pu{1e-4 mol L-1}cdotpu{50 mL}}{pu{0.1 mol L-1}cdotpu{50 mL}} = pu{1e-3}~text{or}~0.1%$$






          share|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thank you! I appreciate your help. I seem to have missed the entire purpose of the titration... so the idea is that you are setting the molar amount of base to the molar amount of acid specifically at the equivalence point, then solving for the original concentration of acid. then you divide the hydrogen ion concentration by this value
            $endgroup$
            – Jon
            Apr 1 at 15:00
















          6












          6








          6





          $begingroup$

          I'm not sure I follow your logic.
          For a monobasic acid S $(ce{HA})$ dissociation degree $α$ is



          $$α = frac{[ce{H+}]}{c_mathrm{a}},$$



          where $c_mathrm{a}$ is the initial concentration of the acid which you are determining via titration with the defined volume of a strong base $V_mathrm{b}$:



          $$c_mathrm{a}V_mathrm{a} = c_mathrm{b}V_mathrm{b} implies c_mathrm{a} = frac{c_mathrm{b}V_mathrm{b}}{V_mathrm{a}}$$



          Finally, taking $V_mathrm{a} = V_mathrm{b} = pu{50 mL}$ (from the figure's caption and equilibrium point) and, as you already assumed from pH, $[ce{H+}] approx pu{1e-4 mol L-1}$:



          $$α = frac{[ce{H+}]V_mathrm{a}}{c_mathrm{b}V_mathrm{b}} = frac{pu{1e-4 mol L-1}cdotpu{50 mL}}{pu{0.1 mol L-1}cdotpu{50 mL}} = pu{1e-3}~text{or}~0.1%$$






          share|improve this answer









          $endgroup$



          I'm not sure I follow your logic.
          For a monobasic acid S $(ce{HA})$ dissociation degree $α$ is



          $$α = frac{[ce{H+}]}{c_mathrm{a}},$$



          where $c_mathrm{a}$ is the initial concentration of the acid which you are determining via titration with the defined volume of a strong base $V_mathrm{b}$:



          $$c_mathrm{a}V_mathrm{a} = c_mathrm{b}V_mathrm{b} implies c_mathrm{a} = frac{c_mathrm{b}V_mathrm{b}}{V_mathrm{a}}$$



          Finally, taking $V_mathrm{a} = V_mathrm{b} = pu{50 mL}$ (from the figure's caption and equilibrium point) and, as you already assumed from pH, $[ce{H+}] approx pu{1e-4 mol L-1}$:



          $$α = frac{[ce{H+}]V_mathrm{a}}{c_mathrm{b}V_mathrm{b}} = frac{pu{1e-4 mol L-1}cdotpu{50 mL}}{pu{0.1 mol L-1}cdotpu{50 mL}} = pu{1e-3}~text{or}~0.1%$$







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Apr 1 at 14:50









          andseliskandselisk

          19k660125




          19k660125








          • 1




            $begingroup$
            Thank you! I appreciate your help. I seem to have missed the entire purpose of the titration... so the idea is that you are setting the molar amount of base to the molar amount of acid specifically at the equivalence point, then solving for the original concentration of acid. then you divide the hydrogen ion concentration by this value
            $endgroup$
            – Jon
            Apr 1 at 15:00
















          • 1




            $begingroup$
            Thank you! I appreciate your help. I seem to have missed the entire purpose of the titration... so the idea is that you are setting the molar amount of base to the molar amount of acid specifically at the equivalence point, then solving for the original concentration of acid. then you divide the hydrogen ion concentration by this value
            $endgroup$
            – Jon
            Apr 1 at 15:00










          1




          1




          $begingroup$
          Thank you! I appreciate your help. I seem to have missed the entire purpose of the titration... so the idea is that you are setting the molar amount of base to the molar amount of acid specifically at the equivalence point, then solving for the original concentration of acid. then you divide the hydrogen ion concentration by this value
          $endgroup$
          – Jon
          Apr 1 at 15:00






          $begingroup$
          Thank you! I appreciate your help. I seem to have missed the entire purpose of the titration... so the idea is that you are setting the molar amount of base to the molar amount of acid specifically at the equivalence point, then solving for the original concentration of acid. then you divide the hydrogen ion concentration by this value
          $endgroup$
          – Jon
          Apr 1 at 15:00




















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