Chemistry experiment: analysis

In our Chemistry lesson on 26th April we carried out two experiments focusing on analysis.

The first experiment involved us coming up with our own method in order to identify five unknown solutions. The first step was to use blue litmus paper to identify which solution was nitric acid as the paper would turn red. Using this solution we then identified the sodium carbonate, as when the nitric acid was added to each solution, the sodium carbonate produced effervescence since carbon dioxide gas was produced. The sodium carbonate solution was then used to  identify the silver nitrate as upon adding, a dirty white precipitate (far right test tube in figure 1) formed while the other solutions showed no reaction. The silver nitrate and nitric acid were then used to identify the two remaining solutions, both of which were halide salts. The formation of a white precipitate indicated the presence of chloride ions and therefore identified sodium chloride (far left test tube in figure 1) while a yellow precipitate showed the presence of iodide ions and so indicated potassium iodide (middle test tube in figure 1).

Fig. 1 Positive analysis tests for experiment 1
Fig. 1 Positive analysis tests for experiment 1

The second experiment focused on identifying two salts consisting of Group 2 cations and which has different solubilities. Figure 2 shows the results, with the far right test tube showing a white precipitate that dissolved in excess ammonia, the second left test tube showing effervescence and the two remaining test tubes showing the formation of white and yellow precipitates.

Fig. 2 Positive analysis results for experiment 2
Fig 2. Positive analysis results for experiment 2

Overall, I think I preferred the first experiment because the fact that you had to come up with your own method meant that you had to think about the experiment more carefully and concentrate on what you were trying to find and what steps you should carry out in which order.

 

 

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