Salts preparation method

SOLUBLE SALT

1)TITRATION
for Sodium.Potassium,Ammonium salt




2)Reaction of acid and insoluble substances




INSOLUBLE SALT

3) precipitation



The above videos are the starting part of the salt preparation.
If they are looking for pure and dry sample of the salt ALWAYS

1) if it is soluble
heat to obtain a saturated solution
cool it to let it crystallise
filter and dry between pieces of filter paper

2) if it is already in solid form
filter and dry between pieces of filter paper

Answers for mock exam paper on Periodic Table and Metals

Water vapour test & Iodine test

Common mistakes

Anions test

1) Carbonate ion test

Observation: Bubbles observed. Test for gas. When gas bubbled in limewater, white ppt formed in limewater.




2) Sulfate ion test

Observation: White ppt formed (barium sulfate)


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3) Chloride ion test

Observation: White ppt formed. (silver chloride)



4) Iodide ion test

Observation: yellow ppt formed. (silver iodide)



5) Nitrate ion test

Observation: Pungent gas evolved turned red litmus paper blue. Ammonia gas produced.

Test for cations using aqueous sodium hydroxide/aqueous ammonia

Read the list of instructions before you view the videos.
Pay attention to the WAY the test is done.

If you use the correct volumes and do the tests in the correct way, you will get the correct observation.

Instructions for doing cation tests:
1. Put about 2cm3 of unknown into a test tube.
2. Do NOT use more than 2cm3.
3. Add A FEW DROPS of aqueous sodium hydroxide/ammonia.
4. Shake the test tube to mix.
5. Observe for ppt.
6. Add aqueous sodium hydroxide/ammonia until it's 3/4 of the test tube. (i.e. excess).
7. Observe whether ppt is soluble in excess or not.


1) Ammonium ion test

Observation: No ppt formed. Ammonia gas is produced on warming. (refer to 'ammonia gas test' video)



2) Calcium ion test

Observation: White ppt formed in aq. sodium hydroxide, insoluble in excess. No visible change in aq. ammonia.



3) Zinc ion test

Observation: White ppt formed in aq. sodium hydroxide, soluble in excess to form colourless solution.
White ppt formed in aq. ammonia, soluble in excess to form colourless solution.



4) Aluminium/Lead ion test

Observation: White ppt. formed in aq. sodium hydroxide, soluble in excess to form colourless solution. White ppt formed in aq. ammonia, insoluble in excess.






5) Iron (II) ion test

Observation: Green ppt formed in aq. sodium hydroxide, insoluble in excess. Green ppt formed in aq. ammonia, insoluble in excess.



6) Iron (III) ion test

Observation: Reddish brown ppt formed in aq. sodium hydroxide, insoluble in excess. Reddish brown ppt formed in aq. ammonia, insoluble in excess.



7) Copper (II) ion test

Observation: Blue ppt formed in aq. sodium hydroxide, insoluble in excess. Blue ppt formed in aq. ammonia, soluble in excess to form dark blue solution.

White ppt vs No ppt formed (solution)

Ppt = SOLID is present



1. Test tube 1 contains a colourless SOLUTION.
2. Test tubes 2, 3 and 4 ALL contain WHITE PPT.
3. There is NO SUCH THING as a "white solution" or a "colourless ppt".

Observations for this experiment:
Test tube 1: Colourless solution formed.
Test tubes 2/3/4: White ppt formed.


SOLUTION = no solid present


1. All these test tubes contain SOLUTIONS.
2. You can tell a test tube contains a solution because there is NO SOLID in it at all.
3. If you are not sure, hold the test tube against white light (e.g. window) or a white piece of paper to see clearer.
4. If after mixing, you get any of the above results, you will describe your observations as:

Test tube 1 = Dark blue solution formed
Test tube 2 = Green solution formed
Test tube 3 = Purple solution formed
Test tube 4 = Orange solution formed
Test tube 5 = Yellow solution formed
Test tube 6 = Pink solution formed
Test tube 7 = Pale blue solution formed

(courtesy of Ms Bernice Chen)