Cation and Anion tests

• Al3+ is present when a white ppt is soluble in excess NaOH(aq) and a white ppt is insoluble in NH3(aq)
• Ca2+ is present when a white ppt is insoluble in NaOH(aq) and there is no ppt in NH3(aq)
• Cu2+ is present when a light blue ppt is insoluble in NaOH and a light blue ppt is soluble to give a dark blue solution in NH3(aq)
• Fe2+ is present when a dirty-green ppt is insoluble which turns reddish-brown in contact with air in NaOH and NH3(aq)
• Fe3+ is present when a reddish-brown ppt is insoluble in NaOH and NH3(aq)
• Pb2+ is present when a white ppt is soluble in NaOH, and a white ppt is insoluble in NH3(aq)
• Zn2+ is present when a white ppt is soluble in NaOH and NH3
• NH4+ is present upon warming and produces a colourless pungent gas which turns moist red litmus paper blue
• NO3- is tested by adding aqueous sodium hydroxide then aluminium powder/foil and warming it. Effervescence of a colourless pungent gas which turns moist red litmus blue is observed, the gas is ammonia.
• CO3 2- is tested by adding any dilute acid except for sulfuric acid. Effervescence of a colourless, odourless gas which when bubbled into limewater forms a white precipitate would be observed
• Cl- is tested by adding dilute nitric acid and then aqueous silver nitrate. a white precipitate is observed.
• I- is rested by adding dilute nitric acid and aqueous silver nitrate. A yellow precipitate is observed
• SO4 2- is tested by adding dilute nitric acid and aqueous barium nitrate/barium chloride. A white precipitate is observed