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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: spickid on September 18, 2008, 11:34:32 PM

Title: Precipitation of salts
Post by: spickid on September 18, 2008, 11:34:32 PM

Quote

Lead(II) nitrate and sodium chloride; Pb2+(aq) + 2Cl-(aq)  PbCl2(s)
 Copper(II) sulfate and ammonium carbonate; No reaction occurs.
Magnesium chloride and sodium hydroxide; Mg2+(aq) + 2OH-(aq)  Mg(OH)2(s)
Ammonium sulfate and barium nitrate; Ba2+(aq) + SO42-(aq)  BaSO4(s)
  Calcium acetate and sodium carbonate; Ca2+(aq) + 2C2H3O2-(aq)  Ca(C2H3O2)2(s)

True or false statements

I used a solubility chart, and they all seem to be TRUE to me.
But it's incorrect. What have I overlooked? thank you!

Title: Re: Precipitation of salts
Post by: AWK on September 19, 2008, 01:44:36 AM

http://en.wikipedia.org/wiki/Copper(II)_carbonate

Title: Re: Precipitation of salts
Post by: spickid on September 19, 2008, 01:54:10 AM

thank you!
So that creates a precipitate. So the answer is false.

The other one that I'm slightly not sure of is Calcium acetate and sodium carbonate; Ca2+(aq) + 2C2H3O2-(aq) --> Ca(C2H3O2)2(s)
It doesn't seem true to to me  :-X

Title: Re: Precipitation of salts
Post by: Borek on September 19, 2008, 02:55:10 AM

You have started with calcium acetate, so it is unlikely as a product. What other combinations of anions and cations can for a salt?

Title: Re: Precipitation of salts
Post by: Arkcon on September 19, 2008, 09:49:58 AM

I gotta say, sadly, you have to re-read the chart more carefully, or get a better chart, or start with some of the general solubility rules.  Simply put some of those are obviously insoluble, based purely on experience.  I would start with the solubility rules, they'll keep you from making gross errors, then you can use the chart for more obscure salts.