Sunday, November 22, 2009

standardization ഓഫ് NaoH

Standardization of NaOH1.
Clean a buret and rinse it with the NaOHyou just prepared.
2. Fill the buret with the NaOH.
3. Weigh a clean dry beaker on a balance.
4. Weigh out 0.2 - 0.4 g of KHC8H4O4 and place it in the beaker you just weighed. Make sure you record the weights!
5. Pour the acid into an Erlenmeyer flask; use a stream of water from the wash bottle to complete the transfer.
6. Dissolve this acid in about 20 mL of the boiled distilled water.
7. Add two drops of the phenolphthalein indicator to the flask.
8. Read the buret and record the initial volume making sure there is not a drop on the tip of the buret; if there is, use an extra beaker to get rid of this drop by touching the side of the beaker to the tip of the buret.
9. Place the Erlenmeyer flask under the buret, and place a piece of white paper under it.
10. Position the tip of the buret so it is just beneath the rim of the flask.
11. Add several mL (probably no more than ten) of base solution (NaOH) rapidly with constant swirling.
12. Close buret stopcock to only allow a rapid stream of drops and swirl; at the site where the solution in the buret drops in the acid solution, you will see a pink color, which will disappear

13. When the pink color lingers longer, close the stopcock on the buret more so that you add a drop and swirl until the color changes before adding another drop.
14. Occasionally wash down the sides of the flask with the wash bottle.
15. Near the end point you will want to use partial drops. To do this, open the stopcock so that a drop forms on the tip of the buret. Close the stopcock and use a stream of water from the water bottle to wash the droplet into the sol.
16. Keep adding base until a very light pink color persists for at least 20 seconds.
17. Record the final buret reading.18. Repeat this procedure at least two more times; repeat the titrations until two values for molarity differ by no more than 1% C.

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