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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: macca69831 on February 14, 2010, 06:33:37 pm

Title: Solubility Help
Post by: macca69831 on February 14, 2010, 06:33:37 pm
When writing a precipitation reaction, how am i supposed to know what to react something with.
E.G Use a solubility table to suggest a compound that could be added to each of the following solutions to produce a precipitate.
a) Na2CO3
b) MgI2
c) NaOH
Is there like a rule that I dont know of that can make this easy. E.g Soluble + soluble= ppt or insol + insol= ppt or soluble + insol= ppt...??
Title: Re: Solubility Help
Post by: vexx on February 14, 2010, 07:11:15 pm
Quote from: macca69831 on February 14, 2010, 06:33:37 pm
When writing a precipitation reaction, how am i supposed to know what to react something with.
E.G Use a solubility table to suggest a compound that could be added to each of the following solutions to produce a precipitate.
a) Na2CO3
b) MgI2
c) NaOH
Is there like a rule that I dont know of that can make this easy. E.g Soluble + soluble= ppt or insol + insol= ppt or soluble + insol= ppt...??


i learnt somewhere on this forum about
'SPANA CHOPS'

Soluable Compounds: (SPANA)
Sodium, Potassium, Ammonium, Nitrate and Acetate

Insoluable (CHOPS):
Carbonate, Hydroxide, Oxide, Phosphate and Sulfide.
The insoluable ones are generally insoluable however if they are with a SPANA ion then they become soluable.

So with a) any compound with XC03 (can't be SPANA) so for example Ba(NO3)2 added to form BaC03
and so on with the others


Edit, it says using a solubility table so just use one of them and i think you get in your exam so don't worry, the above is just if you want to do basic ones without it, but that'd never really happen.
Title: Re: Solubility Help
Post by: Studyinghard on February 14, 2010, 07:19:22 pm
vexx I am pretty sure you dont get the solubility table in the exam. The best but I suppose the hardest way is to remember the solubility table and little tiny points like all group 1 metals are soluble. If you go over your table time and time again by exam time you will remember it like the back of your hand.
Title: Re: Solubility Help
Post by: macca69831 on February 14, 2010, 07:29:50 pm
Ok. But how am i supposed to know what to react with it?
Title: Re: Solubility Help
Post by: Studyinghard on February 14, 2010, 07:39:51 pm
Quote from: macca69831 on February 14, 2010, 07:29:50 pm
Ok. But how am i supposed to know what to react with it?

Once you know the table by heart it comes to you instantly.

a) If you read solubility table you know that Na doesnt make a precipitate with anything. Then you have CO3. There are a few exceptions that are mentioned in the solubility table that are soluble when formed with CO3. Stay away from those and you are good. An easy one is Na2CO3 + Ca(Cl)2 = CaCO3(s) + NaCl (aq)

try b now..
Title: Re: Solubility Help
Post by: vexx on February 14, 2010, 07:48:46 pm
Quote from: Studyinghard on February 14, 2010, 07:19:22 pm
vexx I am pretty sure you dont get the solubility table in the exam. The best but I suppose the hardest way is to remember the solubility table and little tiny points like all group 1 metals are soluble. If you go over your table time and time again by exam time you will remember it like the back of your hand.

Oh well whoops.
You don't even need it though.

It's only really needed for gavimetric analysis where the precipitate formed they generally tell who what it is, otherwise it's pretty simple to figure it out (The other compound formed is NaCl or NaNo3) :p