qualitative analysis Flashcards
how can we identify the present cations in an unknown solution?
by adding aqueous sodium hydroxide or aqueous ammonia
what happens when NaOH(aq) is added to Zn2+?
white ppt, Zn(OH)2 is formed
precipitate dissolves in excess to give a colourless solution
what happens when NH3 is added to Zn2+?
white ppt, Zn(OH)2 formed
precipitate dissolves in excess to give a colourless solution
what happens when NaOH is added to Al3+?
white ppt, Al(OH)3 formed
precipitate dissolves in excess to give a colourless solution
what happens when NH3 is added to Al3+?
white ppt, Al(OH)3 formed
precipitate insoluble in excess
what happens when NaOH is added to Pb2+?
white ppt, Pb(OH)2 formed
precipitate dissolves in excess to give a colourless solution
what happens when NH3 is added to Pb2+?
white ppt, Pb(OH)2 formed
precipitate is insoluble in excess
what happens when NaOH is added to Ca2+?
white ppt, Ca(OH)2 formed
precipitate is insoluble in excess
what happens when NH3 is added to Ca2+?
no precipitate formed
what happens when NaOH is added to Cu2+?
light blue ppt, Cu(OH)2 formed
precipitate is insoluble in excess
what happens when NH3 is added to Cu2+?
light blue ppt, Cu(OH)2 formed
precipitate dissolves in excess to give a dark blue solution
what happens when NaOH is added to Fe2+?
green ppt, Fe(OH)2 formed
precipitate is insoluble in excess
what happens when NH3 is added to Fe2+?
green ppt, Fe(OH)2 is formed
precipitate is insoluble in excess
what happens when NaOH is added to NH4+?
no precipitate formed
when heated, ammonia gas is produced and moist red litmus paper turns blue
what happens when NH3 is added to NH4+?
no reaction