In this experiment you will analyze a solution that may contain some of the foll

Question

In this experiment you will analyze a solution that may contain some of the following anions and cations: SO4, Cl, and NO3 K, NH4, Pb, Fe, Cr, Ca, Ni, and Zn.
1. If you determine that Ca^2+ is present in your unknown, which anions could not be present?
2. If your unknown is a clear, colorless solution, what can you deduce about the cations present in it?
3. If Sulfate is present in your unknown solution, which cation(s) will not be present?
4. If your unknown shows no particular color in a flame test, what would you predict? In this experiment you will analyze a solution that may contain some of the following anions and cations: so ,Cl, and NO, K, NH,, Pb*, Fe, Cr, Ca, Ni, and Zn Pre-Lab Assignment I. If you determine that Ca* is present in your unknown, which anion(s) could not be present 2. If your unknown is a clear, colorless solution, what can you deduce about the cations present in it? 3. If sulfate is present in your unknown solution, which cation(s) will not be present shows no particular color in a flame test, what would you predict? CHI

Explanation / Answer

The second question states that the solution is clear and colourless. This immediately indicates that the solution contains alkaline earth metals like K or Ca or ammonium or plumbous cations. If transition metals are present, then only metals with configuration d5 and d10 which are Fe3+ and Zn2+ respecitvely, are present. In these ions, there are no electronic transitions that absorb in visible light and thus do not produce colour.

1. If Ca2+ is present and the given solution is clear, then anion sulfate cannot be present as the two ions immediately form calcium sulfate, which will instantly precipitate out of the solution. NOTE: The salt has very low solubility in water (0.24g/100mL at STP), if either of the ions are in microscopic quantities, it will be soluble. Hence, the answer is given considering bulk amounts of all ions.

2. Cations K+, Ca2+, NH4+, Fe3+ and Zn2+ can be present in the solution.

3. If sulfate is present in the solution, as mentioned before, calcium will not present. Similarly, considering the possible cations that form water insoluble sulfate salts, Pb2+ cannot be present without precipitation of lead (ii) sulfate.

4. The cation given that do not answer flame test is ammonium ion. Though in certain cases, the test of zinc and lead are quite hard to spot but do give a sliver-white colour upon close observation.

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