Chemistry - Methods of retrieving salts replied by tinuviel07 @ Mon, 21 Apr 2008 13:29:00 +0800

tinuviel07 — Mon, 21 Apr 2008 13:29:00 +0800

copper(II) chloride - soluble

lead bromide - low

potassium chloride - all potassium salts soluble

Chemistry - Methods of retrieving salts replied by UltimaOnline @ Mon, 21 Apr 2008 13:23:29 +0800

UltimaOnline — Mon, 21 Apr 2008 13:23:29 +0800

Titration
When the desired salt is soluble, and can be prepared by using an aqueous acid and an aqueous alkali. eg. Sodium chloride from sodium hydroxide and hydrochloric acid. Titration allows for exact neutralization and hence you get a pure salt without contaimination from acid or alkali.

Ionic Precipitation
When the salt is insoluble, and can be prepared by using two aqueous solutions, that can either be salts, acids or alkalis. Eg. lead(II) sulphate from sulphuric acid or sodium sulphate, and lead(II) nitrate. Filter, the desired salt is the residue, the filtrate solution consists of leftover ions – in this case, HNO3 or NaNO3. Because one salt obtained is aqueous and the other (the desired salt) is solid, you can use filtration to easily separate the salts and prevent contamination of your desired salt (eg. PbSO4) by either the other salt (eg. NaNO3), or any acid (eg. H2SO4 or HNO3) if such is used or produced.

Acid with excess insoluble base/carbonate.
When the salt is soluble, and can be prepared by using an aqueous acid and an insoluble base/carbonate. Eg. copper(II) sulphate from sulphuric acid and copper(II) carbonate or copper(II) oxide. Basically, neutralization occurs, same as titration. Reason for difference between this method and titration is, since the base copper(II) oxide is not soluble and you cannot obtain aqueous copper(II) hydroxide, you use excess of the solid (either the oxide or the carbonate) with limited acid, so that you can easily separate (using filtration) the desired pure aqueous salt, and the excess solid. Hence, like titration, this method has its own way of preventing contaimination of the salt (by using excess solid here).

“These are the salts which I am not able to decide their solubility”.
Google for a list of salts and their solubilities.

“Lastly, are silver nitrate and magnesium sulphate soluble can can be prepared by the acid with excess insouble base/carbonate method?”
If these salts were insoluble, you CANNOT use acid with base/carbonate method. Why not? This is a common exam question. Think about it. (hint : the yield will be low; the reaction will cease very quickly).

“Oh, i forgot to ask, is titration ONLY meant for getting back sodium, potassium and ammonium salts?” Never be a dogmatic student who memorizes notes without understanding. Do not merely memorize “titration ONLY meant for getting back sodium, potassium and ammonium salts”, but UNDERSTAND WHY (why this is given as a useful guideline, NOT a rule to be followed unthinkingly merely for the sake of obeying rules!).

Chemistry - Methods of retrieving salts replied by bonkysleuth @ Sun, 20 Apr 2008 18:01:02 +0800

bonkysleuth — Sun, 20 Apr 2008 18:01:02 +0800

State whether the salts are insoluble or soluble before telling me the possible methods of retrieval of the salts. These are the salts which I am not able to decide their solubility so i ain't sure what method to use. 3 ways to get back the salt, namely titration, precipitation and acid with excess insoluble base/carbonate.

salt : solubility methods of retrieval

copper(II) chloride

lead bromid

potassium chloride

Lastly, are silver nitrate and magnesium sulphate soluble can can be prepared by the acid with excess insouble base/carbonate method?

the equations are as follows: (FOR SILVER NITRATE AND MAGNESIUM SULPHATE)

2HNO3 + MgCO3 -> 2AgNo3 + CO2 + H2O

Magnesium sulphate :

H2SO4 + MgCO3 -> MgSO4 + CO2 + H2O

Oh, i forgot to ask, is titration ONLY meant for getting back sodium, potassium and ammonium salts?

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Chemistry - Methods of retrieving salts replied by tinuviel07 @ Mon, 21 Apr 2008 13:29:00 +0800

Chemistry - Methods of retrieving salts replied by UltimaOnline @ Mon, 21 Apr 2008 13:23:29 +0800

Chemistry - Methods of retrieving salts replied by bonkysleuth @ Sun, 20 Apr 2008 18:01:02 +0800