Chemistry Tests

Flame tests, Precipitate tests, food tests, etc.

Li⁺

Scarlet Red

Na⁺

^(Flame)

Yellow

K⁺

^(Flame)

Lilac

Rb⁺

^(Flame)

Red

Cs⁺

^(Flame)

Blue

Mg²⁺

^(Flame)

No flame colour/ bright light

Ca²⁺

^(Flame)

Brick red

Sr²⁺

^(Flame)

Red

Ba²⁺

^(Flame)

Pale green

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 nitrate. 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. 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.

Unsaturated hydrocarbons test

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 acid 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

Solubility of nitrates?

All nitrates are soluble.

Solubility of group 1 and ammonium ions?

All compounds of group 1 and ammonium ions are soluble.

Solubility of chlorides?

All chlorides except for those of Ag, Pb and Hg are soluble.

Solubility of hydroxides?

All hydroxides are insoluble (except those of group 1, ammonium, barium and strontium). (Calcium hydroxide is 'sparingly' soluble and a solution is known as limewater). Aluminium (also zinc and chromium) hydroxide is amphoteric and dissolves in excess hydroxide

Solubility of metal carbonates?

All metal carbonates (except those of group 1, and ammonium) are insoluble

Insoluble black solid?

might be carbon (graphite), iodine or MnO 2 .

Insoluble yellow solid?

An insoluble yellow solid might be sulphur

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.