What r the 2 alkalis used
Aq sodium hydroxide n aq ammonia
What to look out for when recording
Colour of ppt
Solubility of ppt in excess reagent
How does the reaction for cation happen
Cations + hydroxide ions form insoluble metal hydroxide (appears as ppt)
What is observed when sodium n potassium added to aq sodium hydroxide
No observable change
What is observed when aq ammonia added to sodium or potassium
No observable change
What is observed when aq sodium hydroxide is added ammonium
(on warming)
colourless pungent gas evolved
Gas turns damp red litmus paper blue
Gas is ammonia
What is observed when aq ammonia added to calcium
No observable change ( only seen a bit if high concentration of CA2+ )
What is observed when aq sodium hydroxide added to calcium
White ppt seen
Ppt insoluble in excess aq sodium hydroxide
What is observed when aq sodium hydroxide added to aluminium
White ppt seen
Ppt dissolves in excess aq sodium hydroxide to give colourless solution
What is observed when aq ammonia added to aluminium
White ppt seen
Ppt is insoluble in excess aq ammonia
What is observed when aq sodium hydroxide is added to zinc
White ppt seen
White ppt dissolves in excess aq sodium hydroxide to give colourless solution
What is observed when aq ammonia added to zinc
White ppt seen
Ppt dissolves in excess aq ammonia to give colourless solution
What is observed when aq sodium hydroxide is added to copper
Blue ppt seen
Ppt insoluble in excess aq sodium hydroxide
What is observed when aq ammonia added to copper
Blue ppt seen
Ppt dissolves in excess aq ammonia to give dark blue solution
What is observed when aq sodium hydroxide is added to iron (II)
Green ppt seen
Ppt insoluble in excess aq sodium hydroxide
(Turn reddish brown on standing)
What is observed when aq ammonia added to iron (II)
Green ppt seen
Ppt insoluble in excess aq ammonia
Ppt turn reddish brown on standing
What is observed when aq sodium hydroxide is added to iron (III)
Red brown ppt is seen
Ppt insoluble in excess aq sodium hydroxide
What is observed when aq ammonia added to iron (III)
Red brown ppt seen
Ppt insoluble in excess aq ammonia
Why do some ppt dissolves in excess aq ammonia / aq sodium hydroxide?
Ppt can react further w excess alkali to form complex salt that is soluble
Why can’t aq ammonia be used to test for NH4+
Aq ammonia will produce ammonia upon heating
So production of ammonia cant confirm presence of NH4+ in solution
How to test for carbonate
Add dilute acids
How to test for sulfate
- add dilute nitric acid then aq barium nitrate
OR - add dilute hydrochloric acid then aq barium chloride
How to test for chloride
- add dilute nitric acid then aq silver nitrate
How to test for iodide
Add dilute nitric acid then aq silver nitrate
