ion exchange

Hypothesis

It is expected, that it will be possible to purify contaminated water using ion exchange

Safety assessment

Method

1. 4 test tubes were labelled 1-4 in a test tube rack, identifying which had what solution in it.
2. 40cm³ of the Copper Sulphate and Lead Nitrate solution was poured into a 100cm³ beaker, and from this 2cm³ was measured and put into two test tubes.
3. In the first test tube, 4 drops of the 2M Sodium Hydroxide was added, and the second test tube had 4 drops of the 1M Potassium Iodide.
4. The ion exchange tube was packed with the resin, using the flat end of a glass rod, ensuring that a 2cm gap was left at the top.  This was then attached to a boss and clamp stand, with a 150cm³ beaker placed under the ion exchange tube.
5. Next, the resin was washed with 20cm³ of Nitric acid, which was the measured into a 50cm³ beaker and was then slowly poured into the ion exchange tube.
6. 30cm³ of distilled water was then passed through the tube, washing the resin.
7. Then, 5cm³ of the left over Copper Sulphate and Lead Nitrate solution was poured into the ion exchange tube, removing any of the distilled water that may still be on the resin.
8. Another boss and clamp stand was taken, and a clean test tube was placed under the ion exchange tube, so that its tip was resting on the top of the clean tube.
9. The remaining Copper Sulphate and Lead Nitrate solution was slowly poured through the resin, the filtered solution product being caught in the clean test tube.
10. The other two remaining test tube (labelled 3 and 4), had 2cm³ of the filtered solution poured into them, with 4 drops of Sodium Hydroxide in one of the tubes and Potassium iodide in the other.

Set up of the experiment

Results

The second experiment had two test tubes which contained the solution that had passed through the resin.  The test tube that had the sodium hydroxide in it, turned into a transparent/clear solution.  The test tube that had the potassium iodide in it, the solution turned a transparent/clear solution.  

Interpretation

Going back to the hypothesis stated at the beginning it is now proven that it is possible to purify contaminated water using ion exchange.  The reasons, to suspect that the water was contaminated, were that it was coloured.  At the first test at the start involving the sodium hydroxide, the observations recorded were that it was gelatinous – with a blue precipitate.  The gelatinous product in the test tube shows that copper is present.  The white product is lead sulphate.  The following equation shows that they had ‘swapped partners’: sodium + copper → sodium + sulphate.  From the results of the experiment, it was apparent that the when the Sodium Hydroxide was added to the Lead Nitrate and Copper Sulphate solution, it wasn’t able to dissolve, this gave an end result in the first test tube having a concentrated and chalky result.  This is because hydroxides are insoluble in water, meaning it is unable to dissolve in water.  ().  The second experiment involved the solution being run through the ion resin beads.  The ion resin beads were used to remove the hard metals, and instead it purifies and softens the solution.  The hard metals in the experiment were lead and copper.  When they were passed through the resin, the nitrate and sulphate passed through and released the hydrogen ions.  

Reference:

http://genchem.chem.wisc.edu/lab/CCA/STHTM/NAOH/NAOHCUS2.HTM