Procedure

 

1) Obtained and set up 10 test tubes on a rack

2) Poured 200 mL of deionized water and placed it on the hot plate with a thermometer until it reached 80*C

3) Labeled each test 1-10

 

Procedure 1:

-Measure 1mL of an unknown solution into the test tube.

-Add 2 mL of 6 M NaOH with a plastic pipet into the test tube.

-Waft the test tube to observe the presence of ammonia.

 

Procedure 2:

-Place 2mL of an unknown solution into a test tube.

-Add 2-3 drops of 6 M HCl. Observed if any precipitate formed. If no precipitate forms then save the solution for procedure 6.

-Centrifuge the mixture in a disposable test tube and then add 1 drop of 6 M HCl

-If no precipitate forms then separate supernatant into a separate test tube.

-If precipitate formed, reapeat last two steps until no precipitate forms.

-Label each sample and save the supernatant for procedure 6 and use the precipitate for procedure 3.

 

Procedure 3:

-Add 3-4 mL deionized water to the precipitate from Procedure 2 with clean pipet.

-Heat the test tube, stirring it while in a hot water bath for several minutes.

-After the heating, centrifuge the test tube to separate the supernatant from any remaining precipitate.

-Saved the supernatant for procedure 5 and precipitate for procedure 4.

 

Procedure 4:

-Add 10 drops 6 M ammonia solution to the precipitate from Procedure 3 and stir.

-Add 6 M HCl drop by drop until the precipitate reappears.

 

Procedure 5:

-If the solution from Procedure 3 contains any precipitate, reheat it in the water bath until the precipitate dissolves completely.

-Separate the sample into two test tubes and add several drops of 3 M H2SO4 to one of the test tubes.

-Add a couple of drops of potassium chromate to the second test tube then stir.

 

Procedure 6:

-Add 6 M NaOH to the supernatant from Procedure 2 until precipitate forms.

-Add 0.5 mL more of the NaOH and stir.

-Separate the supernatant from any precipitate and save them for Procedure 11 and 7.

 

Procedure 7:

-Add 3 mL of 6M ammonia and stir well.

-Separate the supernatant and save it for procedure 10 and the precipitate for procedure 8.

 

Procedure 8:

-Add 1 mL of 3% hydrogen peroxide solution to the precipitate from Procedure 7.

-Stir well then heat the solution until no more gas appears.

-Add 3 M H2SO4 by drops until the mixture is acidic.

-Seperate the supernatant and save for procedure 9.

 

Procedure 9:

-Add 2 drops of 0.2 M K4(Fe(CN)6) to the solution from Procedure 8.

 

Procedure 10:

-Add 1 drop of 6 M HCL then add 5 drops of dimethylglyoxime reagent to the solution from Procedure 7.

 

Procedure 11:

-Neutralize the solution from Procedure 6 by adding 3 M H2SO4 and use the pH paper to test the pH after adding each drop.