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ana Chrome File Edit View History Bookmarks Window People Help b O D (a (48% Tue Mar 24 5 24 PM Q C Methoxide lon, CH30 Anex C Chemistry question l Cheg Home l Che x Ath Bb C pt Prob http Sp rnij C https:// mycourses.purdue.edu /bbcswebdav/pid-4873955-odt content 1/courses/isscoursemerge wl 201520 mille201_1419103016745/Concept%2 Q il ER 3. A50-mLsample of a solution containing an unknown weak base was titrated with 0.1000M HCl. The titration curve is shown below. 10 31 10 20 30 40 50 60 70 80 volume HCl added (mL) a. Explain how you would use the titration curve to determine the value of Kb for the unknown weak base b. Explain why the solution is acidic at the equivalence point in the titration. Support your argument (s) with appropriate chemical equations.

Explanation / Answer

From the given graph the points that should be noted are

i) at equivalence point the volume of acid used is 50mL and pH is about 3.3-3.5

ii) at half equivalence point, the volume of acid used , we take as 25mL, the pH is approximately 6.0

iii) At half equivalence theconcentrations of conjugate acid and the remaining weak base are equal, in the buffer formed making the pOH = pKb.

Thus answer for first question

1) pH at half equivalence point = 6.0 = 14

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