Contaminated Water

Apparatus

Method

Method A

I have been given a sample of contaminated water. I must carry out various test to try and discover which contaminant is present in the water.

First I must place a test tube in a rack. Fill it half way with the contaminated water. Add a few drops of barium nitrate to the water. Then record all of the changes observed.

Repeat this method with each of the other three reagents (Silver nitrate, Hydrochloric acid and sodium hydroxide).

Method B

   The contaminated water has been boiled down but the residues still remain. To test the contaminant residues you must:

   Prepare a Bunsen burner on a medium flame. Then heat a flame test wire, which cleans it. Then dip the wire into hydrochloric acid to clean it. Repeat these processes until the wire is completely clean.

     Dampen the end of the flame test wire with some water. Then dip it into the contaminant residues that remain from the boiled water. Place and hold the flame test wire into the flame. Observe and record what colour the flame is that the powder burns.

Results

Part A

    No repeat were required to produce this results as I knew there was only one contaminant and only one chemical used observed any colour change at all.

Part B

    No repeats were necessary in this experiment due to the fact that the flam produced was solely orange and contained no other colours.

Conclusion

    The contaminated water definitely contains sodium. This was due to the fact that when the flame test took place, the flame was clearly orange with no other impurities which guarantees it contained sodium.

     I also tested the solution with barium nitrate. No colour change was observed so I knew that the contaminated water does not contain a sulphate ion. I then tested the water with hydrochloric acid and as no bubbles were produced when it was added, I know the water does not contain a cartbonate. I then tested the solution with silver nitrate, which caused the water to turn cloudy white in colour. As it turned cloudy white, I know that the solution contains chloride.

     With all the tests I have carried out, I can guarantee that the contaminant present in the solution is sodium chloride.

Evaluation

      This experiment used a very simple method, that allowed me to be able to fully understand the experiment and prevent any mistakes. Also, method A was basic repetition so I knew what results to expect.

      This experiment was very easy to carry out. This was due to the fact that the experiment required no measuring of the liquids, as the results do not differ, and no timings were required as we were not testing rate of reaction.

       Problems still however arose from this experiment. Colour change was observed by the human eye, so minute colour changes may be hard to see. Also, people may not see the same colour as was seen by others.

       If I were to do this experiment again, I would try to increase the reliability of the results gathered. For my flame test, I would use cobalt-blue glass to accurately observe the colour of the flame. For my chemical reactions test, I would use a colourimeter to observe the colour change, as it would document all change and would be more precise and reliable than the human eye.