An unknown salt has been spilled in the Tar River and you are charged with deter
ID: 564096 • Letter: A
Question
An unknown salt has been spilled in the Tar River and you are charged with determining whether the salt poses cation tests used the chart below and reported the following results. their water intake. The analyst who performed the Qualitative Amalyis lew Chart foe Catos Buffer After adding 50% NaOH to the salt solution contained in a casserole, the color of the red litmus adhered to the bottom of the watch glass covering the casserole did not change. paper Treatment of 9 drops of fresh salt solution with NIb/NHCI buffer mixture produced a light blue . After adding 12 drops of 3M (NH) CO, to the light blue solution, the solution remained light blue. solution Addition oris drops of 1% dimethylglyoxime to the light blue solution produced a strawberry red precipitate. a) (2 pts) Which cation was present in the salt? Provide the name or the chemical formula: H, and Ca are b) (3 pts) Based on the results above and considering that only the cations Fe", Fe)", N considered safe, should the water intake be closed or not closed? Explain Page 1 of 2Explanation / Answer
a) From the qualitative analysis tests performed, the cation present in water is Ni2+. The reason is the changing of colors when different solutions were added. From the table given, it is clear that the cation is Ni2+. When we see the left hand side of the table, we can see that by addition of NH3 and NH4Cl, if it changed into blue, then it is Ni2+. Further on addition of (NH4)2CO3, if it blue, then it is Ni2+. And in the last step, on addition of dimethylglyoxime, it becomes strawberry red in colour. These all observations prove that Ni2+ is present in the sample.
b) As only Fe2+, Fe3+, NH4+ and Ca2+ are considered safe, so this water should not be used as it contains Ni2+. So, the water intake should be closed.
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