Chemical tests

• react with acid (HNO3) • effervescence

• add Ba2+(aq) ions • form a white precipitate (BaSO4 is insoluble) DONT USE BaCl2 (otherwise you will mess up halide results)

Ag+(aq) + X-(aq) –> AgX(s)

Carbonate –> no other ion produces effervescence Sulfate –> must confirm there is no carbonate (or completely react carbonate ions) as BaSO4 also forms a white precipitate which would give a false result (filter our ppt before doing halide test) Halide test –> Ag2CO3 and Ag2SO4 both form precipitates

• 2,4-DNPH • orange precipitate forms

• mix original sample with Tollens’ reagent • silver mirror will form if an aldehyde is present

[Ag(NH3)2]OH

Ag+ (aq) + e- –> Ag (s) - Ag forms silver mirror aldehyde + [O] –> carboxylic acid

• filter, dry and recrystallise the orange precipitate • find the melting point • compare value to one in a data book

• mix with Na2CO3 • effervescence • only organic compounds acidic enough to react with carbonates

NH4+(aq) + OH-(aq) –> NH3(g) + H2O(l)

• AgCl dissolves in dilute NH3 • AgBr dissolves in concentrated NH3 • AgI insoluble in concentrated NH3