IGCSE ION TESTS

carbonate, CO3^2−

• Test: Add dilute acid, then test for carbon dioxide gas.

• Result: Effervescence; carbon dioxide produced.

chloride, Cl^− (in solution)

• Test: Acidify with dilute nitric acid, then add aqueous silver nitrate.

• Result: White precipitate (ppt.).

bromide, Br^− (in solution)

• Test: Acidify with dilute nitric acid, then add aqueous silver nitrate.

• Result: Cream precipitate (ppt.).

iodide, I^− (in solution)

• Test: Acidify with dilute nitric acid, then add aqueous silver nitrate.

• Result: Yellow precipitate (ppt.).

nitrate, NO3^− (in solution), test + result

• Test: Add aqueous sodium hydroxide, then aluminium foil; warm carefully.

• Result: Ammonia gas produced.

sulfate, SO4^2− (in solution), test + result

• Test: Acidify with dilute nitric acid, then add aqueous barium nitrate.

• Result: White precipitate (ppt.).

ammonium, NH4^+, test with NaOH (sodium hydroxide) + test with (NH3) aqueous ammonia

• Test with NaOH (sodium hydroxide): Ammonia gas produced on warming.

• Test with NH3 ( aqueous ammonia): No effect.

calcium, Ca^2+, test with NaOH + test with aqueous ammonia

• Test with NaOH: White precipitate, insoluble in excess.

• Test with NH3: No precipitate or very slight white precipitate.

copper(II), Cu^2+, test with NaOH + NH3

• Test with NaOH: Light blue precipitate, insoluble in excess.

• Test with NH3: Light blue precipitate, soluble in excess, giving a dark blue solution.

iron(II), Fe^2+

• Test with NaOH: Green precipitate, insoluble in excess; precipitate turns brown near surface on standing.

• Test with NH3: Same as NaOH test.

iron(III), Fe^3+

• Test with NaOH: Red-brown precipitate, insoluble in excess.

• Test with NH3: Same as NaOH test.

zinc, Zn^2+

• Test with NaOH: White precipitate, soluble in excess, giving a colourless solution.

• Test with NH3: Same as NaOH test.