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Lab1 Titration

The document outlines a procedure for determining the concentration of acetic acid using titration with standardized NaOH. It details the preparation of NaOH and potassium acid phthalate (KHP) solutions, followed by the titration process with phenolphthalein as an indicator. The calculations for determining the acetic acid content are also provided, along with important notes for conducting the experiment accurately.

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Anny
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21 views2 pages

Lab1 Titration

The document outlines a procedure for determining the concentration of acetic acid using titration with standardized NaOH. It details the preparation of NaOH and potassium acid phthalate (KHP) solutions, followed by the titration process with phenolphthalein as an indicator. The calculations for determining the acetic acid content are also provided, along with important notes for conducting the experiment accurately.

Uploaded by

Anny
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Determination of Concentration of Acidic Acid

Principle:
COOK COOK
+ NaOH + H2O
COOH COONa

Apparatus and reagents


Analytical balance, buret (50 ml), pipets (25 ml), conical flask (250 ml), graduated
cylinders(100 ml, 10 ml), beaker (400 ml), reagent bottles (500 ml), volumetric flask
(250 ml). NaOH, Potassium Acid Phthalate (KHP), phenolphthalein indicator (0.1%
ethanol solution), acidic acid solution.

Standardization of 0.1 M NaOH.


(1) Preparation of NaOH Solution:
Weight out 1.2g NaOH approximately, add about 300 mL of deionized water, dissolve
completely. Keep the cap tightly screwed onto the plastic bottle except when
transferring some to your burette in order to minimize absorption of atmospheric
carbon dioxide. In similar manner, you should also have a burette cap on the top of the
burette for the same reason.
(2) Preparation of Potassium Acid Phthalate (KHP) Standard Solution.
The molecular weight of KHP is 204.22. Accurately (to 0.1 mg) weigh by difference a
quantity of KHP (oven-dried at 110ºC for 1-2 hr) close to this amount into a weighing
paper. KHP is dissolved completely in beaker. Transfer the KHP quantitatively with
glass rod into a 250-mL volumetric flask. Rinse the last traces from the glass rod and
the beaker with a water bottle. Carefully dilute to volume, and mix thoroughly.

(3) Standardization of NaOH solution.


Standardize the 0.1 M NaOH solution you prepared by means of a conventional
acid-base titration using phenolphthalein indicator.

1
1. Fill a 50-mL burette in proper manner with the prepared NaOH solution.
2. Pipet 25 mL of the KHP standard solution into a 250-mL conical flask. Add 2 drops
of phenolphthalein indicator, and titrate carefully to the first permanent light pink
color.
3. Do at least 2 more replicate titrations. The values should agree to within ± 0.5%
RSD. If not, titrate another replicate sample or two.
4. Calculate the exact molarity of the NaOH solution.

C NaOH = 1000 * WKHP 25


*
V NaOH * M KHP 250

2 Titration of Acidic Acid


Rinse the buret with NaOH solution for 3 times. Carefully pipet 25 mL of acidic acid
solution into a 250-mL conical flask. Add 2 drops of phenolphthalein indicator, and
titrate with NaOH carefully to the first permanent light pink color. Repeat for 3 times.
Calculate the CH3COOH content per 100 ml acidic acid according to the following
equation. Calculate the average value.

C NaOH * VNaOH * M CH3COOH


ω CH3COOH% (W/V) =
* 100
25 * 1000

(MCH3COOH)=60.05

Note:
 Weight NaOH with small beaker, do not use weighting paper.
 Before filling the buret, rinse it 3 times with the titrate.
 If there are air bubbles in the buret, turn on the tap to make bubbles out.
 Label the three conical flasks.
 For the repeated experiment, the titration should be started from zero mark

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