A student in the laboratory finds three bottles with no labels. Each bottle contains a white solid powder. Using qualitative analysis, design an experiment the student could perform to determine which elements are present in each of the bottles. Be sure to include posible outcomes.

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I would label the bottles A, B and C.  I would use a sample of each material to make a solution, and test each solution for condutivity.  Ionic compounds form solutions that conduct electricity, covalent compounds do not.  It might also be possible that the compound(s) were not water soluble.b

I could mix samples of each solution with each other and observe if a reaction occurs, what kind of reaction it is, and whether I can recognize any of the products. 

I could also test samples of each solution with indicators, e.g. litmus to see if they are acids or alkalines, or test for the presence of specific metals or polyatomic ions.  Based on which elements trigger displacement reactions with each solution.  Without knowing more about the compounds, I can only speculate as to what the reactions would be. 

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A student in the laboratory finds three bottles with no labels. Each bottle contains a white solid powder. Using qualitative analysis, design an experiment the student could perform to determine which elements are present in each of the bottles. Be sure to include possible outcomes.

Let's say that the three bottles contain Fe(NO3)3, BaCl, and AgNO3.  These are iron (III) nitrate, barium chloride, and silver nitrate.  All three of these are white solids that dissolve in water.  We could come up a with a series of precipitation tests to determine which cation is in which bottle.  Based on the results of these tests, we will be able to determine the identities of the solids.

We know that silver chloride is highly insoluble in water.  So if we reacted an aqueous solution of each of the chemicals with a dilute solution of hydrochloric acid (HCl), the one with Ag+ in it will form AgCl and precipitate as a solid.  The other two samples will give no chemical reaction.  So we have identified which powder is AgNO3.

We know that barium sulfate is highly insoluble in water.  So if we reacted an aqueous solution of each of the chemicals with a dilute solution of sulfuric acid (H2SO4), the one with Ba2+ in it will form BaSO4 and precipitate as a solid.  The other two samples will give no chemical reaction. So we have identified which powder is BaCl.

We know that iron (III) hydroxide is insoluble in water. So if we reacted an aqueous solution of each of the chemicals with a dilute solution of sodium hydroxide (NaOH), the one with Fe3+ in it will form Fe(OH)3 and precipitate as a solid. The other two samples will give no chemical reaction. So we have identified which powder is Fe(NO3)3.

So we have now designed a qualitative analysis experiment in which we have matched up the identities of the three starting solids.

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Three bottles, each containg white solid powder. Using qualitative analysis design an experiment to determine which elements are present in these bottles?

Tough question, Khoob! You need to dissolve the powders in water, and then design a flowchart that will sort the ions in the different solutions based on their solubility characteristics. Here's a list of solubilities to test for:

Ions in Group I: Ag+, Hg22+, Pb2+-will precipitate in 1 M HCl

Ions in Group II: Bi3+, Cd2+, Cu2+, Hg2+, (Pb2+), Sb3+ and Sb5+, Sn2+ and Sn4+ -will precipitate in 0.1 M H2S solution at pH 0.5

Ions in Group III: Al3+, (Cd2+), Co2+, Cr3+, Fe2+ and Fe3+, Mn2+, Ni2+, Zn2+ - will precipitate in 0.1 M H2S solution at pH 9

Ions in Group IV: Ba2+, Ca2+, K+, Mg2+, Na+, NH4+
Ba2+, Ca2+, and Mg2+ will precipitate in 0.2 M (NH4)2CO3 solution at pH 10

Once you have narrowed down the possibilities for each powder, you could try a flame test to make identifications within the groups.

To test for the anions, there are some indicator based tests you could include at this link.

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