How do you test for carbonates
add any dilute acids and observe effervescence
bubble the gas through limewater, as carbon dioxide is produced, it turns limewater cloudy
Cl + Na₂CO₃ → 2NaCl + H₂O + CO₂
How do you test for a sulphate
Acidified BaCl₂
if sulphates are present, then a white precipitate
Ba²⁺(aq) + SO4²⁻(aq) → BaSO₄(s).
How do you test for halogens
Silver nitrate/ AgNO₃
Chlorides produce a white precipitate
Bromides produce a cream precipitate
Iodides produce a yellow precipitate
Ag⁺ + X⁻ → AgX
Why is do you need to distinguish carbonates from halogens first
nitric acid will react with carbonates and produces effervescence rather than reacting with halogens and producing a precipitate
Why can’t sulfuric acid be used to acidify a barium chloride when testing for sulphates
it would form a precipitate
How can you distinguish between halogens after adding silver nitrate
silver chloride precipitate will dissolve in dilute ammonia
silver bromide precipitate will dissolve in concentrated ammonia
silver iodides don’t react with ammonia
what should the series of tests be for halogens, sulphates and carbonates and why
carbonates, sulphates and then halides
BaCO₃ and BaSO₄ are insoluble
how can you test for NH₄⁺
react it with warm NaOH
forms NH₃ gas
turns damp red litmus paper blue
How do you test for aldehydes
Tollen’s reagent
forms a silver mirror
ketones can’t be oxidised by Tollens
How do you test for carbonyls
add 2,4 DNP
forms an orange precipitate
What reacts with acidified dichromate to turn it from orange to green
Cr³⁺
aldehydes
what reacts with bromine water do decolourise it
alkenes
what turns acidified dichromate orange after refluxing it
Cr₂O₇²⁻
Ti³⁺
pale purple
V²⁺
pale purple
Cr²⁺
blue
Mn²⁺
pale pink
Fe²⁺
grey
Co²⁺
bright pink
Ni²⁺
green
V³⁺
green
Cr³⁺
green
Fe³⁺
yellow
Co³⁺
green
