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I need help interpreting lab results = mystery alkaline earth halide

I need help interpreting lab results = mystery alkaline earth halide - Chemistry Forum

I need help interpreting lab results = mystery alkaline earth halide - Chemistry Forum. Discuss chemical reactions, chemistry.


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Old 09-29-2003, 03:16 AM
Sarah
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Default I need help interpreting lab results = mystery alkaline earth halide



I need help interpreting this lab result.

Taking an alkaline earth halide hydrate (an unknown white powder), I dehydrated
the chemical over a bunsen burner, so that I was left with only an alkaline
earth halide.

i have determined the amount of chemical (6.1 g) before dehydration, and the
amound of chemical (5.15) after.

Then, I did a flame test in which I took the dehydrated alkaline earth halide
and placed it over a bunsen fire.

The fire turned lime green when in contact with the powder.

Then, I took some alkaline earth halide, and rehydrated it to create an
aqueous solution. I made two test tubes of this solution.

In one, I added drops of Na2CrO4 (Sodium Chromate), forming (I think) a white
percipitate that begun to create a snow globe atmosphere.
In the other, I added drops of AgNo3 (Silver Nitrate), forming a milky lime
green/yellow percipitate (close to the color of a sick person's mucas).

Those percipitates may be the other way around -- I will double check to make
sure.

So the question is - What alkaline earth halide has these properties?
Where can I find information about percipitates where I can tell if
AgNo3 mixes with such and such alkaline earth halide, then the halide must be...

After, I will do analysis to decide exactly how much water is in the oringinal
hydrate, etc.

Thank You,
Sarah
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Old 09-29-2003, 10:54 PM
Steve Turner
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Default I need help interpreting lab results = mystery alkaline earth halide

[Only registered users see links. ] (Sarah) wrote:


If you're sure that what you have is an alkaline earth halide, the
above observation alone could be sufficient to identify the cationic
substituent of your unknown. It will depend on how you did the flame
test. If you used a copper wire, for example, the copper by itself
will impart a green color to the flame (thereby invalidating the
test). If you used a platinum or nichrome wire, then your color
observation should be true and you can consult a table of flame colors
for the alkaline earth salts.


The color of the silver halide precipitate (note the spelling) will
give you a clue as to the identity of the halide. Silver chloride is
white (when freshly precipitated); silver bromide is pale yellow, and
silver iodide is distinctly yellow.


How about your textbook or lab manual?

Steve Turner

Real address contains worldnet instead of spamnet
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