Chemsheets AS006 (Electron arrangement) 21/04/2019 HALIDE ION TESTS

IT IS THE SILVER NITRATE SOLUTION THAT REACTS WITH THE SAMPLE SOLUTION TEST FOR HALIDE IONS (Cl- ; Br- ; I-) ADD DILUTE NITRIC ACID FOLLOWED BY SILVER NITRATE SOLUTION TO THE SAMPLE SOLUTION NITRIC ACID IS ADDED TO REMOVE IMPURITES IT IS THE SILVER NITRATE SOLUTION THAT REACTS WITH THE SAMPLE SOLUTION A COLOURED PRECIPITATE OF SILVER HALIDES FORM

NOTE// The nitric acid is added to remove CO32- (carbonate ions) and OH- ions (hydroxide ions) which would otherwise precipitate with Ag+ ions and ∴ show incorrect results by masking the desired observations

i.e. HALIDE ION COLOUR OF PRECIPITATE FORMED NAME OF PRECIPITATE FORMED Chloride ion (Cl-) White Silver chloride Bromide ion (Br-) Cream Silver bromide Iodide ion (I-) Yellow Silver iodide Cl- Br- I-

Ionic equations Below are the ionic equations which describes the precipitation reaction which take place: The coloured precipitates which form From the sample From the silver nitrate The state symbols are crucial, as you need to show that the silver halides (AgCl etc) are formed as solids i.e. (s). This is why you see precipitates in the reactions! Cl-(aq) Ag+(aq) Ag Cl(s) + Br-(aq) Ag+(aq) Ag Br(s) + I-(aq) Ag+(aq) Ag I(s) +

The main problem with this test is that it is very difficult to distinguish between the precipitate colours particularly between AgBr and AgI so another confirmatory test must be carried out To carry out a confirmatory test ammonia solution is added

Action of dilute NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) Cl–(aq) Br–(aq) I–(aq)

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate AgF is soluble Cl–(aq) Br–(aq) I–(aq) © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Br–(aq) I–(aq) © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Soluble in dilute NH3(aq) AgCl(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Cl–(aq) Br–(aq) I–(aq) © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Soluble in dilute (aq) ammonia AgCl(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Cl–(aq) Soluble in dilute (aq) NH3 Br–(aq) I–(aq) © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Soluble AgCl(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Cl–(aq) Br–(aq) Ag+(aq) + Br–(aq) → AgBr(s) cream ppt I–(aq) © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Soluble in dilute (aq) NH3 AgCl(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Cl–(aq) Br–(aq) Ag+(aq) + Br–(aq) → AgBr(s) cream ppt Insoluble in dilute (aq) NH3 I–(aq) © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Soluble in dilute (aq) NH3 AgCl(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Cl–(aq) Br–(aq) Ag+(aq) + Br–(aq) → AgBr(s) cream ppt Insoluble in dilute (aq) NH3 Soluble in conc. (aq) NH3 AgBr(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Br–(aq) I–(aq) © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Soluble in dilute (aq) NH3 AgCl(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Cl–(aq) Br–(aq) Ag+(aq) + Br–(aq) → AgBr(s) cream ppt Insoluble in dilute (aq) NH3 Soluble conc. (aq) NH3 AgBr(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Br–(aq) I–(aq) Ag+(aq) + I–(aq) → AgI(s) yellow ppt © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Soluble in dilute (aq) NH3 AgCl(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Cl–(aq) Br–(aq) Ag+(aq) + Br–(aq) → AgBr(s) cream ppt Insoluble in dilute (aq) NH3 Soluble in conc. (aq) NH3 AgBr(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Br–(aq) I–(aq) Ag+(aq) + I–(aq) → AgI(s) yellow ppt © www.chemsheets.co.uk AS 1067 3-July-2015

Action of dilute NH3(aq) Action of conc. NH3(aq) Halide ion Action of AgNO3(aq) Action of dilute NH3(aq) Action of conc. NH3(aq) F–(aq) No precipitate Cl–(aq) Ag+(aq) + Cl–(aq) → AgCl(s) white ppt Soluble in dilute (aq) NH3 AgCl(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Cl–(aq) Br–(aq) Ag+(aq) + Br–(aq) → AgBr(s) cream ppt Insoluble in dilute (aq) NH3 Soluble in conc. (aq) NH3 AgBr(s) + 2 NH3(aq) → [Ag(NH3)2]+(aq) + Br–(aq) I–(aq) Ag+(aq) + I–(aq) → AgI(s) yellow ppt Insoluble in conc. (aq) NH3 © www.chemsheets.co.uk AS 1067 3-July-2015