Solubility Help

[macca69831]

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...??

[vexx]

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.

[Studyinghard]

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.

[macca69831]

Ok. But how am i supposed to know what to react with it?

[Studyinghard]

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..

[vexx]

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