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Topic: HOw to identify these solutions>  (Read 30641 times)

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xxfunguy007xx

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HOw to identify these solutions>
« on: April 04, 2005, 02:20:33 PM »
I have to identify these solutions, Ba(NO3)2, FeCl3, LiOH, KSCN, H2SO4, AgNO3, Na2CO3, Al(NO3)3, CuSO4, SrCL2, NH3, ZnSO4, CoCl2., and KI through mixing them together, flame test, ph, smell, etc for lab. How do I do that. My teacher told me that mixing one with another will create color change and percipitate. Can anyone help me with this. Thanks you

Offline AWK

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Re:HOw to identify these solutions>
« Reply #1 on: April 05, 2005, 05:01:59 AM »
smell - NH3
pH - basic  - LiOH and Na2CO3 - test both in flame test
pH - highly acidic - H2SO4
color - CuSO4, CoCl2, may be FeCl3 (it depends on concentration)
and so on!
AWK

Offline hmx9123

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Re:HOw to identify these solutions>
« Reply #2 on: April 05, 2005, 06:20:43 AM »
In addition to what AWK said about IDing by sight, you should make a list of cations and anions.  Then take a look at which ones you could mix to get a precipitate and compare to your list of unknowns.  You should know the solubilities by your solubility rules.  I used to TA a lab like this for undergrads.  It's like a big logic puzzle.  Here's the idea:

Your list consists of Ba+2 among all the other cations.  You know from your solubility rules that if you mix the barium cation with a sulfate, it will give a precipitate.  You look through and see that if you were to mix the barium solution with sulfuric acid, copper sulfate or zinc sulfate you'd get BaSO4 as a precipitate.  Then you take a look at the other anions.  Ask yourself, 'Does barium form an insoluble compound with: nitrate, chloride, hydroxide, thiocyanate or carbonate?"  Repeat for each cation/anion pair.

That will get you a long way, but there's a few tricks in here.  You have to be careful of redox reactions.  Take a look at the reduction and oxidation potentials of each of these that has multiple oxidation states (like copper, etc.).  You may very well get a redox reaction that changes oxidation states of your compound.

In addition, you need to be careful with the aluminum nitrate.  Not that it's toxic, but it can be a little tricky.  The sodium carbonate should tell you if you have an acid, because it bubbles CO2.  However, aluminum nitrate may give some bubbles, too, although not like sulfuric acid.  This comes from the fact that aluminum hydroxide is slightly soluble, causing the aluminum ion to pull some hydroxide from water, forming a nearly invisible gelatinous aluminum hydroxide precipitate.  Of course, you may not note any of this, depending on the quality of water that was used to make the solution, but it's something to keep in mind.

Good luck.
« Last Edit: April 08, 2005, 12:28:36 AM by hmx9123 »

Offline Donaldson Tan

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Re:HOw to identify these solutions>
« Reply #3 on: April 05, 2005, 11:22:10 PM »
I have to identify these solutions, Ba(NO3)2, FeCl3, LiOH, KSCN, H2SO4, AgNO3, Na2CO3, Al(NO3)3, CuSO4, SrCL2, NH3, ZnSO4, CoCl2., and KI through mixing them together, flame test, ph, smell, etc for lab. How do I do that. My teacher told me that mixing one with another will create color change and percipitate. Can anyone help me with this. Thanks you

theoretically speaking, your post may be locked for not showing that you've attempted.

i will use two tables to analyse the problem. the first table tabulates the possible observation when you mix 2 substances together, whereas the 2nd table tabulates the observation when you mix component A with component B, and etc. Then I will compare both tables to identify the required substance.

To simplify the process of identification, some compounds can be identified easily without the need of rigourous analysis. For example, your sense of smell should be able to identify the pungent aq ammonia, and you can identify by sight that FeCl3 must be the yellow solution. Add some ammonia to a small sample of the yellow solution to confirm its identity. you should get a brown precipitate. Once you have identified FeCl3, you canidentify KSCN because Fe3+ forms a purple complex with SCN-
« Last Edit: April 08, 2005, 12:29:40 AM by hmx9123 »
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Garneck

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Re:HOw to identify these solutions>
« Reply #4 on: April 06, 2005, 08:51:26 AM »
I have to identify these solutions, Ba(NO3)2, FeCl3, LiOH, KSCN, H2SO4, AgNO3, Na2CO3, Al(NO3)3, CuSO4, SrCL2, NH3, ZnSO4, CoCl2., and KI through mixing them together, flame test, ph, smell, etc for lab. How do I do that. My teacher told me that mixing one with another will create color change and percipitate. Can anyone help me with this. Thanks you

First things that come to my mind:
1. CuSO4 - blue solution
2. Once you've identified H2SO4 in a pH test, you can identify Na2CO3 --> adding H2SO4 will cause CO2 bubbles to appear
3. You can use that to identify Ba(NO3)2 and SrCL2 - both give carbonate precipitate. You can then identify them, for example, by flame tests. Ba2+ gives a green flame, while Sr2+ as far as I remember, a red flame.


@geodome: Fe3+ actually gives a "bloody red" complex with SCN-

xxfunguy007xx

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Re:HOw to identify these solutions>
« Reply #5 on: April 17, 2005, 03:14:11 PM »
Also ZnSO4 I am really not sure exspically Al(NO3)3

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