Exam (elaborations) Ahip

AQA A-LEVEL CHEMISTRY CHEMICAL TESTS

test for Carbon Dioxide (CO2 ) - ANSWER-turns limewater milky (sparingly soluble
Ca(OH) 2 forms insoluble CaCO3 )

Chlorine (Cl2 ) test - ANSWER-bleaches damp litmus paper (Cl2 reacts with water to
form HCl and HOCl)

Hydrogen (H2 ) test - ANSWER-pops with a lighted splint

Oxygen (O2 ) test - ANSWER-relights a glowing splint

Carbonate (CO 3 2- ) test - ANSWER-add dilute acid; effervescence, carbon dioxide
produced

Sulfate (SO4 2- ) test - ANSWER-add dilute nitric acid then aqueous barium nitrate.
Gives white precipitate

Chloride (Cl - ) test - ANSWER-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 - ANSWER-add dilute nitric acid then aqueous silver nitrate. Gives
cream precipitate. Dissolves in concentrated ammonia but not in dilute ammonia

Iodide (I - ) test - ANSWER-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 - ANSWER-add aqueous sodium hydroxide gives green precipitate,
insoluble in excess

Iron III (Fe 3+ ) test - ANSWER-add aqueous sodium hydroxide gives orange/brown
precipitate, insoluble in excess

Copper (Cu 2+ ) test - ANSWER-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 - ANSWER-add aqueous sodium hydroxide gives white
precipitate, insoluble in excess.

Aluminium (Al 3+ ) test - ANSWER-add aqueous sodium hydroxide gives white
precipitate which dissolves in excess