Testing for Anions and Cations
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if a silver halide precipitate dissolves in the presence of dilute ammonia, what is the halide
chloride ion
how can you test for halide ions
add hno3 then add silver nitrate white precipitate is chloride, cream is bromide, yellow is iodide
if a silver halide precipitate dissolves in the presence of concentrated ammonia, what is the halide
bromide
which silver halide doesnt dissolve in ammonia at all
silver iodide
how can you test for carbonate ions
add hcl, if effervescence then present, bubble the gas through limewater and if it goes cloudy then carbonate ions are present
how can you test for sulfate ions
add barium chloride, white precipitate means sulfate is present
how can you test for nitrate ions
nitrate ions will never form any kind of precipitate
how can you test for hydroxide ions
turn damp red litmus paper blue and are alkaline so will turn universal indicator blue
what should you add to a compound to test which cation is present
sodium hydroxide solution
which ion forms a green ppt with NaOH
iron (II)
which ion forms a blue ppt with NaOH
copper (II)
which ion forms a brown/red ppt with NaOH
iron (III)
which ions can form a white precipitate with NaOH not in excess
calcium, magnesium and aluminium
if a white precipitate forms with NaOH, how can we distinguish between the cation
add excess NaOH if it dissolves then aluminium is present if not then its either calium or magnesium then u need to use flame tests, calcium produces a brick red flame
what cations are present if no precipitate forms with NaOH
ammonium, strontium, barium, g1 metals
what colour is lithium flame
red
what colour is sodium flame
yellow
what colour is potassium flame
lilac
what colour is calcium flame
brick red
how can we test for ammonium ions after adding sodium hydroxide
warm the solution the gas released will turn red litmus paper blue
what gas is release when you warm an ammonium compound and sodium hydroxide solution give the ionic equation
ammonia gas NH4+ + OH- —-> NH3 + H2O
whats a cation
a positive ion
whats an anion
a negative ion