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Unit 19 Assignment 2 - Practical Chemical Analysis
Finding the concentration of phosphate ions in a solution produced by the action
of the enzyme phosphatase
Within this experiment, an unknown concentration of a solution that contained
phosphate ions was tested to find the true concentration of each sample that
was made.
The equipment that was used within this experiment is shown below:
Equipment
- Burette
- Boss
- Clamp
- Stand
- 10cm3 pipette
- 5cm3 pipette
- 1cm3 pipette
- Spatula
- 7 x Boiling tubes
- Tongs
- Test tube rack
- Bunsen burner
- Tripod
- Gauze
- Matches
- Heatproof mat
- Colorimeter
- 7 x Curettes
- 100cm3 volumetric flask
- Ammonium molybdate solution
- Ascorbic acid
- 250cm3 beaker
- Distilled water
Method
1) Firstly, a clean burette that was fitted onto a boss and clamp stand was
filled with 50cm3 of a standard potassium dihydrogenphosphate solution.
,Unit 19 Assignment 2 - Practical Chemical Analysis
2) A 100cm3 volumetric flask was then used to measure out 15cm 3 of the
phosphorus solution. The volumetric flask was further filled up to the
100cm3 line with distilled water.
3) Next, a boiling tube was placed into the tube rack. The 5cm 3 pipette was
used to measure out 5cm3 of the phosphate solution from the volumetric
flask into the boiling tube. The 10cm 3 pipette was used to measure out
10cm3 of deionised water into the boiling tube. The 1cm 3 pipette was used
to measure out 1cm3 of ammonium molybdate solution into the test tube.
Finally, a spatula measure of ascorbic acid crystals was added into the
boiling tube.
4) Then, the boiling tube was placed into a 250cm 3 beaker and the beaker
was filled ¾ of the way with distilled water.
5) The Bunsen burner was then plugged into the gas source and the flame
was lit by using a match. A heatproof mat was placed onto the counter
and a tripod and gauze was placed onto it. The beaker was placed on top
of the tripod and the Bunsen burner was placed underneath the beaker to
bring the water to a boil.
, Unit 19 Assignment 2 - Practical Chemical Analysis
6) Once the water had boiled, the boiling tube was removed from the beaker
by using the tongs and placed into the tube rack to allow it to cool.
7) This process was repeated another 5 times – each test completed used
2.5cm3 less of the phosphorus solution.
8) Once all seven of the tests were complete and the boiling tubes had
cooled down, a sample from each test tube was transferred into a curette
and tested using the colorimeter. This was able to provide the absorbance
levels from each sample which could be used to find the rough
concentration of X.
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