Chemical tests Flashcards
test for Carbon Dioxide (CO2)
turns limewater milky (sparingly soluble Ca(OH) 2 forms insoluble CaCO3 )
Chlorine (Cl2 ) test
bleaches damp litmus paper (Cl2 reacts with water to form HCl and HOCl)
Hydrogen (H2 ) test
pops with a lighted splint
Oxygen (O2 ) test
relights a glowing splint
Carbonate (CO 3 2- ) test
add dilute acid; effervescence, carbon dioxide produced
Sulfate (SO4 2- ) test
add dilute nitric acid then aqueous barium chloride. Gives white precipitate
Chloride (Cl - ) test
add dilute nitric acid then aqueous silver nitrate. Gives white precipitate. Dissolves in dilute ammonia to give colourless solution (of [Ag(NH 3 ) 2 ] + )
Bromide (Br - ) test
add dilute nitric acid then aqueous silver nitrate. Gives cream precipitate. Dissolves in concentrated ammonia but not in dilute ammonia
Iodide (I - ) test
add dilute nitric acid then aqueous silver nitrate. Gives yellow precipitate. Does not dissolve in either concentrated or dilute ammonia
Iron II (Fe 2+ ) test
add aqueous sodium hydroxide gives green precipitate, insoluble in excess
Iron III (Fe 3+ ) test
add aqueous sodium hydroxide gives orange/brown precipitate, insoluble in excess
Copper (Cu 2+ ) test
add aqueous sodium hydroxide gives blue precipitate, insoluble in excess. Or add ammonia: gives a blue precipitate which dissolves in excess to give a blue solution
Calcium (Ca 2+ ) test
add aqueous sodium hydroxide gives white precipitate, insoluble in excess.
Aluminium (Al 3+ ) test
add aqueous sodium hydroxide gives white precipitate which dissolves in excess
H + (any acid) test
turns blue litmus red or makes sodium carbonate effervesce (makes CO 2 gas)
H2O test
- turns white anhydrous copper (II) sulphate into blue hydrated copper (II) sulphate. 2. It also turns blue anhydrous cobalt (II) chloride into pink hydrated cobalt (II) chloride reaction is reversible, colour changes reversed when hydrated salts are heated.
Test for Unsaturated hydrocarbons
turns bromine water from orange to colourless.
Test for aldehydes
produces a silver mirror from a colourless solution of Tollens’ reagent (or produces a red precipitate from blue coloured Fehling’s solution (needs heat))
Tests for organic (and other) acids (carboxylic acid)
they release CO2 (bubbles of gas are observed) when shaken with sodium carbonate solution
Test for acyl chloride
gives misty fumes with water
Test for alcohol
add acidified potassium dichromate (K2Cr2O7) orange to green (Cr3+)
Manganate ion change of colour
when reduced, goes from deep purple to colourless
Manganate ion change of colour
when reduced, goes from deep purple to colourless
test for sulfate ion
add nitric acid (removes carbonate ions so no other ppt forms), add barium chloride, barium sulfate forms, white ppt.
test for amines
turns litmus paper blue (naturally basic)
test for arene
burn in air. produces smokey flame and soot.
