Thursday, May 26, 2011

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.




1 comment:

  1. what can i put as a discussion for this exp help please

    ReplyDelete