1) if the same experiment had to be done using an indicator phenolphthalein (cha
ID: 1051206 • Letter: 1
Question
1) if the same experiment had to be done using an indicator phenolphthalein (changes color at pH= 8-10) or bromocresol green (pH=3-5), which one should you use and why? 2) where would you find the buffer region for this curve? Label the appropriate location. 2. Titration of a 25 mL sample of a nicotinic acid was performed against 0.15 M KOH solution. (4 Volume of KOH(mL) 14 pH 12 1.96 10 2.22 2.46 4 7 10 2.77 3.064 3.29 12 14 16 17 18 20 25 0 10 15 20 25 30 3.6 4.26 11.08 11.67 12.05 12.4 vol of Na 0HExplanation / Answer
Hi,
In any titration to find out the end point we use indicater.
In given titration with weak organic acid with KOH (strong) will give end point in basic medium the Potasium nicotiniate again hydrolyse to give OH- and solution becomes basic unlike nutral in stong acid-base titration. So, the indicater which shows colour change in basic pH range will be preferred. So, the choice is phenolphthalein.
From the figure the portion from pH 2.0 to pH 4.0 ( near to the point where suddent increase in pH). When a weak acid is being nutralised, the formation of conjugate base increase and hence acts as buffer untill the base over comes buffer capacity.
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