8 For the following titration curve 5. a. Fill in the blanks in the title with a
ID: 692838 • Letter: 8
Question
8 For the following titration curve 5. a. Fill in the blanks in the title with appropriate terms regarding the strength and acid or base character of the analyte and titrant. Titration of 25.0 mL of with 0.10 M 10 15 20 25 30 35 40 45 50 volume of 0.10 M added (mL) b. Determine the value of pkx of the analyte (I'm purposely "mislabeling" this term to avoid giving away part of the answer in part a) c. Which indicator makes more sense to use for this titration, methyl red or phenolphthalein? Defend your choice with a logical explanation.Explanation / Answer
a. This is strong acid and strong base titration curve. In this titration of 25 ml of strong HCl with 0.1 M of Na0H strong base.
b.For the dissociation of any strong acid,
HCl(aq) H+ (aq) + Cl– (aq)
there is an acid dissociation constant,
Ka=[H+][Cl-] / [HCl]
This can be rearranged to solve for [H+]
: [H+]=Ka [HCl]/ [Cl-]
Using the definition of pH, this equation can be rearranged as follows:
PH=- log H30+
PH=-log Ka-log [HCl]/[Cl-]
PH=PKa+log [Cl-]/[HCl]
at equivalance point
PH=7=PKb
c. In this titration of strong HCl with Na0H strong base the phenolphtahlein is the best indicator. In basic it shows pink colour and in acidic it is colourless.Also methyl red is best wich shows red color in acidic and colourless in basic.
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