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2g) tests for ions and gases (Cl-, Br-, I- (Br (Cream ppte, AgBr), Cl…
2g) tests for ions and gases
Flame tests
method
Dip a piece of nichrome wire in a small beaker of HCL
Dip the wire into a watch glass of solid
Put the wire into a roaring flame
Clean the wire by dipping back in HCl and then back into the flame
results
Na - Orange
K - Lilac
Li - Red
Ca2 - Orange - Brick Red
Testing for NH4
method
Pour about 3cm in depth of NH4Cl(aq) into a test tube
Add a little NaOH(aq) to the NH4Cl
heat gently for a few seconds
Moisten a piece of red litmus paper and hold it in the mouth of the test tube
results
Red litmus paper turns blue
Cations
are positive ions
Anions
are negative ions
Cu2, Fe2 and Fe3 using sodium hydroxide
Method
Add a few drops of NaOH(aq) to sample that's being tested
Observe the colour of any precipitate formed
Results
Precipitation
reaction = A reaction of two solutions which produce an insoluble solid
NH4+
Add NaOH(aq), heat fully, hold damp red litmus paper to top of test tube
Litmus paper turns blue
Cl-, Br-, I-
i) Add dilute NO3 to make acidic (this removes impurities which can react with AgNO3
ii) Add AgNO3 Solution
Br
Cream ppte
Cl
White ppte
I
Yellow ppte
Add marble chips to HCl and test gas produced by bubbling through lime water
Limewater goes cloudy
Add 2cm3 of Sodium sulphate, then add 1cm3 nitric acid, Add 1cm3 barium chloride
White ppte
H2
Lit splint test
Squeeky pop
O2
Glowing splint test
relights splint
CO2
Bubble gas through limewater
cloudy limewater
NH3
Damp red litmus paper test
paper turns blue
Cl2
Damp blue Litmus paper
paper turns red and is bleached
