IDENTIFYING COMPOUNDS Flashcards
How do you identify an alkane
under UV light, add bromine, orange bromine is decolourised and steamy acidic fumes of HBr form
How do you identify an alkene
in the dark, add bromine, orange bromine water decolourises
How do you identify a carbonate
add dilute HNO3 (inorganic acid), if carbonate ions are present, effervescence occurs due to CO2 being formed
How do you identify a sulfate
Add dilute HNO3 first to remove any carbonate ions that may give a false positive result.
Add aqueous barium ions, if sulfate is present, a white ppt of BaSO4 forms
How do you identify a halide
Add dilute HNO3 first to remove any carbonate ions that may give a false positive result.
Add aqueous barium ions, to remove any sulfate ions that may give a false positive result.
Add aqueous silver nitrate:
white ppt of AgCl soluble in dilute + conc NH3
cream ppt of AgBr insoluble in dilute + soluble in conc NH3
yellow ppt of AgI insoluble in dilute + conc NH3
How do you identify ammonium cations
Add aqueous NaOH then warm mixture. If a vapour that turns damp red litmus paper blue, then this is due to ammonia gas being formed from the ammonium ions
How do you identify a phenol
add bromine, bromine is decolourised and a white ppt forms
How do you identify an aldehyde/ketone
Add 2,4-DNPH
orange/yellow ppt forms
How do you identify an aldehyde specifically
warm with Tollens’ Reagent
shiny silver mirror on inside of test tube forms
