test for anions

Question 1

carbonate ion CO3 2-

Answer 1

barium Ba: white ppt, soluble in acid to form a colourless solution
lead Pb: white ppt, soluble in acid to form a colourless solution
silver Ag: white ppt, turns pale yellow on standing, soluble in acid to form a colourless solution

test:
add dilute acid
pass the gas given off into limewater Ca(OH)2

observation:
effervescence observed. colourless, odourless gas evolved forms a white precipitate (CaCO3) when bubbled into limewater. Gas is CO2

Question 2

sulfate ion SO4 2-

Answer 2

test:
add aq Ba(NO3)2 / BaCl2 (OR Pb), then dilute HNO3 / HCl

observation:
white ppt, insoluble in acid

Question 3

chloride ion Cl-

Answer 3

test:
add aq AgNO3 (OR Pb), then dilute HNO3

observation:
white ppt, insoluble in acid
(Ag) soluble in aq NH3 to form a colourless solution

Question 4

iodide ion I-

Answer 4

test:
add aq AgNO3 (OR Pb), then dilute HNO3

observation:
yellow ppt, insoluble in acid
(Ag) insoluble in aq NH3

Question 5

nitrate NO3-

Answer 5

test:
add aq NaOH, then aluminium/zinc foil or Devarda’s alloy, then warm the mixture.
test gas with moist red litmus paper

observation:
effervescence observed. colourless and pungent gas evolved turns moist red litmus paper blue. gas is ammonia gas NH3