Chem-Distinguish salts?

1.
Sodium Chloride, Magnesiumsulphate, Ammonium Chloride

Using separately each of the three salts, perform a flame test. Only sodium chloride give a bright yellowflame, but the other two give no particular flame colour.

Dissolve separately each of the two unidentified salts in distilled water toform a solution. Add separately sodium carbonate solution to each of the twosolutions.
Magnesium sulphate: A white precipitate is formed.
MgSO4(aq) + Na2CO3(aq) → MgCO3(s) + Na2SO4(aq)
Ammonium chloride: There is no observable change.


= = = = =
2.
Calcium Carbonate, SodiumCarbonate, Sodium Nitrate, Calcium Chloride

Using separately each of the four salts, perform a flame test. Two of the salts give brick red flames, andthe rest two give bright yellow flames.

Add separately the two salts giving brick red flames to dilute hydrochloric acid.
Calcium carbonate: Colourless gas bubbles are given off.
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l)+ CO2(g)
Calcium chloride: There is no observable change.

Add separately the two salts giving bright yellow flames to dilute hydrochloricacid.
Sodium carbonate: Colourless gas bubbles are given off.
Na2CO3(s) + 2HCl(aq) → 2NaCl(aq)+ H2O(l) + CO2(g)
Sodium chloride: There is no observable change.


= = = = =
3.
Calcium Nitrate, PotassiumNitrate, Potassium Sulphate, Calcium Hydroxide

Using separately each ofthe four salts, perform a flame test. Twoof the salts give brick red flames, and the rest two give lilac flames.

Test each of the two salts giving brick red flames with a moist red litmuspaper.
Calcium nitrate: There is no observable change.
Calcium hydroxide: The red moist litmus paper turns blue.

Test each of the two salts giving lilac flames with a moist red litmus paper.
Potassium nitrate: There is no observable change.
Potassium hydroxide: The red moist litmus paper turns blue.

2011-06-06 22:58:38 補充：
There are more than one method for each question.

In Q.1, if only NaOH solution is used, heat is necessary for testing ammonium salt.

In Q.3, you can do so, but you would do an extra step (adding BaCl2/HCl) than usual.

2011-06-06 22:59:09 補充：
請看意見欄