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Process of Titration

The process of titration is carried out to find the volume of one solution required to react completely with a certain known volume of solution of some other substance. In the acid-base titration acid is usually put in the burette and the alkali in the flask. The process of titration is carried out as under:

l . Wash the burette with water and then rinse it with the acid solution (or the solution to be used).

2. With the help of a funnel fill the burette with the acid solution. Flush out air bubbles from the jet of the burette. Adjust the level of the burette so that the nozzel tip just enters the mouth of the conical flask. Place a white tile or white paper sheet under the conical flask.

3. Rinse the pipette with alkali solution and pipette out 25 cm3 of the alkali solution into a washed conical flask.

4. Add t-2 drops of indicator the solution in conical flask and note the colour.

5. Carefully note the initial reading of the burette and record it.

6. With the neck of the flask in one hand, open the stopcock with the other hand, as shown in Fig. 23.13. Add the acid solution to the flask in small volumes at anyone time. Swirl the conical flask during and after each addition of acid solution.

7. Continue the addition of small volumes of the acid solution until the colour of the indicator just changes.

8. Record the final burette reading to the two decimal places, carefully estimating the second decimal place.

9. The solution from the titration flask is thrown away and the titration flask is washed thoroughly first by keeping it under tap water and then with a little of distilled water. Do not rinse the titration flask.

10. Repeat the titration using another 25 cm3 of alkali solution in the washed conical flask. Note the initial reading of the burette. Release acid into the alkali until you are about 1 cm3 away from the end point. Now add the acid drop wise with swirling until the last single drop brings about permanent change in the colour of indicator. Read the burette. Note down the final burette reading.

11. Repeat the step 10 until you get three values for the volume of acid used which differ by not more than 0.20 cm3.

12. Average any two or more consistent titre values to find the volume of acid used for neutralization of 25 cm3 of the alkali solution.