| Pages:
1
2
3 |
a.dunn.wa
Harmless
Posts: 21
Registered: 31-5-2012
Member Is Offline
Mood: No Mood
|
|
That first video is pretty neat. Do you still think it could be/is sodium acetate? I feel like since HCl + Unknown --> a strong, vinegar smell it
must be the acetate..I don't know any others that would do that
|
|
|
Hexavalent
International Hazard
Posts: 1564
Registered: 29-12-2011
Location: Wales, UK
Member Is Offline
Mood: Pericyclic
|
|
I think the first sentence on the link you provided is a typo.
The best bet would be to try and test the pH again in your lab, perhaps there was just something wrong with the indicator sample you used? Or the
reaction vessel? Or maybe you even used the wrong sample to begin with . . .even scientists make mistakes sometimes
There is a good chance that it is sodium acetate.
By adding HCl, you would get acetic acid and sodium chloride. This reaction is favored because of the formation of a weaker acid.
NaC2H3O2 + HCl --> HC2H3O2 + NaCl
If it's a net ionic equation you want, just eliminate the spectator ions, which in this case are Na+ and Cl-, the only ions that remain in solution:
H+ + C2H3O2- --> HC2H3O2
Do you think it's sodium acetate trihydrate or anhydrous? If its the trihydrate, add some to a test tube and test the MP by heating very slowly with a
Bunsen burner, maybe even in a water bath if you can. The trihydrate melts at 58*C, which is surprisingly low for an ionic solid.
[Edited on 7-6-2012 by Hexavalent]
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
|
|
|
Mixell
Hazard to Others
Posts: 449
Registered: 27-12-2010
Member Is Offline
Mood: No Mood
|
|
C:
Probably Sn II chloride, as the teacher said it has chloride (or iodide) ions in it, and it's a reducing agent.
A:
If it bubbles on contact with acid, it is sodium carbonate. Sodium acetate is not acidic, it is basic.
Also, you contradict yourself:
"Unknown letter A- nothing note worthy happened when mixed with NaOH, K2SO4 or AgSO4
Appeared to dissolve in each"
"For Unknown A: we guessed sodium sulfate. He said that it does have Sodium, but is not sulfate. Our new hypothesis is that is is sodium acetate,
because it has a distinct, vinegar-like odor, when mixed with HCl. Other pieces of supporting evidence are that the compound is ACIDIC, burns
yellow/orange (sodium indication), and forms a white precipitate with AgNO3"
Sodium nitrate is fairly soluble, so it will not form a precipitate, so did the solution form a precipitate with silver ions or not?
You don't have any acidic sodium salt (unless the sodium phosphate is NaH2PO4) that will form a precipitate with silver. The only acidic salt of
sodium you have is the bisulfate.
B:
The basic (and not reducing) sodium salts you have are: phosphate, borate, citrate, oxalate, carbonate (not including acetate).
Test it with acid, if bubbles are formed, it is the carbonate.
|
|
|
a.dunn.wa
Harmless
Posts: 21
Registered: 31-5-2012
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Hexavalent  | I think the first sentence on the link you provided is a typo.
The best bet would be to try and test the pH again in your lab, perhaps there was just something wrong with the indicator sample you used? Or the
reaction vessel? Or maybe you even used the wrong sample to begin with . . .even scientists make mistakes sometimes
There is a good chance that it is sodium acetate.
By adding HCl, you would get acetic acid and sodium chloride. This reaction is favored because of the formation of a weaker acid.
NaC2H3O2 + HCl --> HC2H3O2 + NaCl
If it's a net ionic equation you want, just eliminate the spectator ions, which in this case are Na+ and Cl-, the only ions that remain in solution:
H+ + C2H3O2- --> HC2H3O2
Do you think it's sodium acetate trihydrate or anhydrous? If its the trihydrate, add some to a test tube and test the MP by heating very slowly with a
Bunsen burner, maybe even in a water bath if you can. The trihydrate melts at 58*C, which is surprisingly low for an ionic solid.
[Edited on 7-6-2012 by Hexavalent] |
Your right about the typo, sorry about that. Here's the link I intended to paste:
http://www.youtube.com/watch?v=epd-DAE_sEI
This is sort of as much for my partner to see as well, because this looks exactly like ours...
We will definitely test the pH again tomorrow. Chances are something just went wrong or we made a mistake, happens a lot to us in chemistry
How would one go about determining/deciding if a compound is anhydrous or trihydrate? I would suspect it to be somewhat hydrated because we have been
opening the container quite a bit and I'm sure some of the water from the air was captured/sucked up by the compound (espec. since its hygroscopic).
Either way, we may just try to find the melting point as we have 50 minutes, and we may not have that many other tests to run.
|
|
|
a.dunn.wa
Harmless
Posts: 21
Registered: 31-5-2012
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Mixell | C:
Probably Sn II chloride, as the teacher said it has chloride (or iodide) ions in it, and it's a reducing agent.
A:
If it bubbles on contact with acid, it is sodium carbonate. Sodium acetate is not acidic, it is basic.
Also, you contradict yourself:
"Unknown letter A- nothing note worthy happened when mixed with NaOH, K2SO4 or AgSO4
Appeared to dissolve in each"
"For Unknown A: we guessed sodium sulfate. He said that it does have Sodium, but is not sulfate. Our new hypothesis is that is is sodium acetate,
because it has a distinct, vinegar-like odor, when mixed with HCl. Other pieces of supporting evidence are that the compound is ACIDIC, burns
yellow/orange (sodium indication), and forms a white precipitate with AgNO3"
Sodium nitrate is fairly soluble, so it will not form a precipitate, so did the solution form a precipitate with silver ions or not?
You don't have any acidic sodium salt (unless the sodium phosphate is NaH2PO4) that will form a precipitate with silver. The only acidic salt of
sodium you have is the bisulfate.
B:
The basic (and not reducing) sodium salts you have are: phosphate, borate, citrate, oxalate, carbonate (not including acetate).
Test it with acid, if bubbles are formed, it is the carbonate.
|
We re-did the test today with the AgNO3 and we did observe a white precipitate for unknown A. We must've either misread, or goofed the test before,
because it is a pretty clear white precipitate.
We will also re-test the pH tomorrow, there is probably a good chance it is basic, and seems logical that it would be, so we will re-test that
tomorrow.
As far as B goes we will test it with an acid (again) tomorrow. Now that I think about it, when we tested it with H2SO4 it DID form bubbles
eventually, but we were so fixated on the potential smell of vinegar we did not make a note of it...it did have an relatively strong odor to it, but
may not have been vinegar. By bubbles forming, do you mean as in bubbles boiling at the top of the liquid, or more at the bottom. I remember observing
bubbles forming at the bottom of the liquid..
Thanks for the help guys!!! I feel like we're really close to getting this nailed! 
|
|
|
Mixell
Hazard to Others
Posts: 449
Registered: 27-12-2010
Member Is Offline
Mood: No Mood
|
|
Add the solid to H2SO4, it should fizz and bubble vigorously, you will not be able to miss it!
If the solution of A is neutral (low molar concentration), it can still be sodium acetate if there is an unmistakable smell of vinegar.
[Edited on 7-6-2012 by Mixell]
|
|
|
a.dunn.wa
Harmless
Posts: 21
Registered: 31-5-2012
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Mixell | Add the solid to H2SO4, it should fizz and bubble vigorously, you will not be able to miss it!
If the solution of A is neutral (low molar concentration), it can still be sodium acetate if there is an unmistakable smell of vinegar.
[Edited on 7-6-2012 by Mixell] |
Hmmm...when we added unknown B to H2SO4 it didn't seem to fizz and bubble vigorously, but we will try it again tomorrow! If it doesn't fizz and bubble
vigorously, what other tests could we perform to figure out which one it is?
|
|
|
Mixell
Hazard to Others
Posts: 449
Registered: 27-12-2010
Member Is Offline
Mood: No Mood
|
|
If it did form a precipitate with AgNO3, then you can try to do some titrations (with appropriate indicators) do determinate what kind of sodium salt
that is.
If the pH is neutral, it can be the sodium chloride/iodide/bromide, to determinate exactly which, you will need to oxidize he halides and check which
is which (take a look at one of my previous replies to your thread).
|
|
|
a.dunn.wa
Harmless
Posts: 21
Registered: 31-5-2012
Member Is Offline
Mood: No Mood
|
|
Well, we turned our lab in on Friday. We got 3 of the 4 right. Just in case any of you are interested these are the correct results:
Unknown A = sodium acetate
Unknown B = sodium nitrite
Unknown C = tin ii chloride
Unknown D = iron ii sulfate
We got A, C, and D completely right and we got 1/2 credit on B for getting the first half right (pretty sweet deal). We ended up getting a 95% and we
really owe it to you guys for all your help/assistance.
|
|
|
Hexavalent
International Hazard
Posts: 1564
Registered: 29-12-2011
Location: Wales, UK
Member Is Offline
Mood: Pericyclic
|
|
You're welcome, glad you got such a good grade! Congrats!
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
|
|
|
| Pages:
1
2
3 |
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
