Topic 9a- Chemical analysis / tests for ions
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Flame test: Lithium
Red
Flame test: Sodium
Orange/Yellow
Flame test: Potassium
Lilac
Flame test: Calcium
Brick red/orange
Flame test: Barium(?) (not on spec)
apple green
Why is only a small amount of NaOH is used?
So the metal hydroxide precipitates In excess NaOH some of the precipitates may dissolve
Flame test: Copper
green/blue
What is used to test for cations?
NaOH (sodium hydroxide)
Sodium hydroxide test: copper
Light blue precipitate, remains in excess (insoluble)
Sodium hydroxide test: Ammonium ions (NH4 (+))
No precipitate, gentle heating produces ammonia gas that can be tested for with red litmus paper, turning blue
Sodium hydroxide test: Calcium
White precipitate, remain in excess (insoluble)
Sodium hydroxide test: Aluminium
White precipitate, dissolve in excess
Sodium hydroxide test: Iron(II)
Green precipitate, remains in excess (insoluble)
Sodium hydroxide test: Iron(III)
Red-brown precipitate, remains in excess (insoluble)
Test for carbonate ions
Add dilute acid, effervescance seen, CO2 produced, lime water test
test for sulfate ion
Add dilute HCl and aqueous barium chloride, white precipitate of barium sulfate formed
How to test for halide ions?
Add dilute nitric acid (HNO3) then add silver nitrate solution (AgNO3), forms silver halide precipitate forms
What colour is silver chloride?
White
What colour is silver bromide?
Cream
What colour is silver iodide?
Yellow