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This is the answer to chapter 20, problem number five, from the mcmurray organic chemistry textbook.
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In this problem, we're asked to calculate some percentages of dissociated and undissociated species of acid in two different solutions.
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And so basically, we are just going to use the henderson -hasselbach equation, and we're just going to plug in the information that we've been given and then solve.
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For the variables that we haven't been given.
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So the first thing that i'm doing here is just writing down what we know for solution a.
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So it's a 0 .001 molar solution, the pca of glycolic acid.
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We are given as 3 .83.
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Okay.
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And then the ph of the solution is 4 .50.
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Okay.
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So we have these three.
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Pieces of information.
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We're just going to plug them in where they go.
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And so the henderson -hasselback equation is going to be log of the conjugate base.
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So log a minus over concentration of h .a.
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Equals ph minus pca.
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Okay? and so we have a lot of those variables already.
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So we can substitute in the ph and the pca.
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So ph is 4 .50.
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Our pqa is 3 .83.
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And so that comes out to 0 .67.
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Okay.
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And so now what we need to do is to get this out of log form.
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So that's going to look like the concentration of the conjugate base over the concentration of the acid is going to be equal to the anti -log of 0 .67.
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And so if you're doing this with a graphing calculator, you would use the 10 up -carat button.
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So 10 .0 .67.
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And i should say negative.
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Okay.
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And so that equals 4 .68.
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Or wait, no, not negative.
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Sorry.
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I don't know why i threw a negative sign in there.
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So that equals 4 .6.
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There we go.
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4 .68.
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I apologize.
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Having some lag issues.
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Oh, man.
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Okay.
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So 4 .68.
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And so then we can say that the concentration of the conjugate base is equal to 4 .68 times the concentration of the conjugate base.
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Okay.
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And so from here, we know percentage -wise that the concentration of the conjugate base and the concentration of the acid, the sum of these two values, has to equal 100%.
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And so we can then plug in what we've done so far.
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So, ha.
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And then we're going to substance.
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Constitute this 4 .68 times h .a...