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ემზადებით გამოცდისთვის? მოემზადეთ ამ გაკვეთილის დახმარებით შემდეგ თემაზე: Studying for the AP Chemistry exam?
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- The pH of the soft drink is 3.37 after the addition of the potassium sorbate. Which species, the sorbic acid or the sorbate ion, has a higher concentration in the soft drink. Justify your answer. So, this is related to the question we've been doing because the sorbate ion, this is what happens when you put potassium sorbate and it dis-associates in a solution. So the concentration of the sorbate ion is the same thing as the concentration. One way to think about it, is going to be the same as the concentration of your potassium sorbate. So if we're thinking about titrating potassium sorbate, which we've been doing in the last several parts of the problem. At what point do you have an equal concentration of potassium sorbate and sorbic acid. Well you have equal concentrations at the half-equivalence point. We marked that out when we figured it out in the last few parts of this problem. And the half-equivalence point happened at a pH of, we actually figured it out before, 4.77. So we could say... "half-equivalence point "of titration "of potassium sorbate "with hydrochloric acid "happens at a pH of," let me write that pH of, "4.77." And that's the point at which you have equal concentrations of, so we can put this in parentheses, "can be viewed as point "where we have equal "concentrations, "of C6H7O2 minus," and ascorbic acid, "HC6H7O2." "pH of 3.37 is lower and will thus," or we could say, "will happen beyond "half-equivalence point." Beyond half-equivalence point. So, concentration of the sorbic acid is higher. "So concentration "of sorbic acid, "HC6H7O2, is higher." When you're starting off, if you're doing a titration. Your concentration of potassium sorbate, it'll be higher then you keep titrating and it keeps reacting with the hydrochloric acid. You get to the half-equivalence point where these two things are going to have equal concentrations. Then if you keep titrating it, well then you're going to become more acidic and your going to have a higher concentration of the sorbic acid. So one way to think about, actually let me underline that whole part, "so concentration of sorbic acid is higher." That's the main thing that they're asking for. But the way to think about this soft drink is something it might not have, and obviously people are sitting there and titrating every soft drink. But you can kinda view this soft drink as well it got that point after a theoretical titration that got us past the... half-equivalence point. And so therefore, most of our things that we care about is in the form, is in the acid form versus the conjugate base. Most of the sorbic acid is in its acid form. Or I guess you could say it the other way. Most of the sorbate has become the conjugate acid.