testing and identifying anions

Testing and Identifying Halide Ions

Aim:To identify the conclusive chemical tests for Halide ions.

Chloride Cl-1;Bromide Br-1;Iodide I-1

•Add about 2ml of aqueous chloride to a test tube

•Add an equal volume of dilute HNO3

•Add a few drops of silver (I) nitrate to the tube

•Pour half of the contents of the tube into a clean test tube

•To the 1st tube add dilute ammonia until no further change

•To the second tube add CONC AMMONIA until there is no further change – Do this in a fume cupborad

•Repeat with aqueous solutions of bromide and iodide

Results Table

Halide Ion HNO3 then AgNO3

Action of dilute NH3 on product

Action of conc NH3 on product

Cl-1

Br-1

I-1

Results Table

Halide Ion HNO3 then AgNO3

Action of dilute NH3 on product

Action of conc NH3 on product

Cl-1 White ppt White ppt dissolves

Br-1

I-1

Results Table

Halide Ion HNO3 then AgNO3

Action of dilute NH3 on product

Action of conc NH3 on product

Cl-1 White ppt White ppt dissolves White ppt dissolves

Br-1

I-1

Results Table

Halide Ion HNO3 then AgNO3

Action of dilute NH3 on product

Action of conc NH3 on product

Cl-1 White ppt White ppt dissolves

Br-1 Cream ppt

I-1

Results Table

Halide Ion HNO3 then AgNO3

Action of dilute NH3 on product

Action of conc NH3 on product

Cl-1 White ppt White ppt dissolves

Br-1 Cream ppt No reaction Cream ppt dissolves

I-1

Results Table

Halide Ion HNO3 then AgNO3

Action of dilute NH3 on product

Action of conc NH3 on product

Cl-1 White ppt White ppt dissolves

Br-1 Cream ppt Insoluble Cream ppt dissolves

I-1 Yellow ppt Insoluble insoluble

Ionic Equations for the reaction

• Sodium chloride + Silver nitrate

• NaCl + AgNO3

• Repeat for Sodium Bromide and Silver iodide as above

Sulphate SO42- and Sulphite SO3

2-

Place 2ml of aqueous sulphate in a test tube.

Add a few drops of barium chloride

Add 1ml of HCl Dilute and shake the mixture vigorously

Leave the tube to stand

Repeat the experiment with a sample of aqueous sulphite – do in fume cup board, Test the gas evolved with acidified dichromate paper

Results Table

Anions Action of BaCl2 followed by HCl

SO42-

SO32-

Results Table

Anions Action of BaCl2 followed by HCl

SO42- White ppt of BaSO4 that does not

redissolve in acid

SO32- Gas evolved with pungent odour – SO2..

It turns acid dichromate paper from orange to green ( test for SO2)

Carbonate CO32- and Hydrogen

Carbonate HCO3-1

Add 1 ml of sodium carbonate to a test tube – add a few drops of HCl

Repeat the experiment with aqueous potassium hydrogen carbonate

Record the results in the table

Add a few drops of Barium chloride

Results

Anion Reaction with HCl followed by Barium chloride

CO32-

HCO3-1

Results

Anion Reaction with HCl followed by Barium chloride

CO32- Gas evolved – CO2

White ppt formed

HCO3-1 Gas evolved – CO2

No ppt formed

Nitrate ion NO3-1

Place together in a test tube a small amount of sodium nitrate (V) and a piece of Al foil.

Add about 5ml of aqueous sodium hydroxide solution

If no reaction takes place – carefully warn the tube in a water bath

Test the gas evolved using damp red litmus paper

Results table

Ion Observation

NO3-1 Pungent gas evolved.

Turns red litmus blue – Alkaline gas – Ammonia.

Formed by the reduction of the nitrate ion.

Summary of results

Name of ion Formula Test Result

Chloride

Bromide

Iodide

Sulphate

Sulphite

Carbonate

Hydrogen carbonate

Nitrate

Summary of results

Name of ion Formula Test Result

Chloride Cl-1

Bromide Br-1

Iodide I-1

Sulphate (IV) SO42-

Sulphite (VII) SO3-1

Carbonate CO32-

Hydrogen carbonate HCO3-1

Nitrate NO3-1

Summary of results

Name of ion Formula Test Result

Chloride Cl-1 Acidified silver nitrate

Solubility with ammonia

White ppt of AgCl soluble in dil NH3

Bromide Br-1 Acidified silver nitrate

Solubility with ammonia

Cream ppt of AgBr soluble in conc NH3

Iodide I-1 Acidified silver nitrate

Solubility with ammonia

Yellow ppt of AgI insoluble in excess NH3

Sulphate (IV) SO42-

Sulphite (VII) SO3-1

Carbonate CO32-

Hydrogen carbonate

HCO3-1

Nitrate NO3-1

Summary of results

Name of ion Formula Test Result

Chloride Cl-1 Acidified silver nitrate

Solubility with ammonia

White ppt of AgCl soluble in dil NH3

Bromide Br-1 Acidified silver nitrate

Solubility with ammonia

Cream ppt of AgBr soluble in conc NH3

Iodide I-1 Acidified silver nitrate

Solubility with ammonia

Yellow ppt of AgI insoluble in excess NH3

Sulphate (IV) SO42- Solution of barium chloride or

nitrate.If ppt forms add dil HClWhite ppt of BaSO4

insoluble in acid

Sulphite (VII) SO3-1 As above Gas evolved

SO2.Test with dichromate paper turning from orange to green,

Summary of results(2)

Name of ion Formula Test Result

Carbonate CO32-

Hydrogen carbonate

HCO3-1

Nitrate NO3-1

Summary of results(2)

Name of ion Formula Test Result

Carbonate CO32- Dilute HCl followed by BaCl2

Hydrogen carbonate

HCO3-1 Dilute HCl followed by BaCl2

Nitrate NO3-1

Summary of results(2)

Name of ion Formula Test Result

Carbonate CO32- Dilute HCl followed by BaCl2 White ppt of BaCO3

formed and gas evolved

Hydrogen carbonate

HCO3-1 Dilute HCl followed by BaCl2 Gas evolved

No ppt.

Nitrate NO3-1

Summary of results(2)

Name of ion Formula Test Result

Carbonate CO32- Dilute HCl followed by BaCl2 White ppt of BaCO3

formed and gas evolved

Hydrogen carbonate

HCO3-1 Dilute HCl followed by BaCl2 Gas evolved

No ppt.

Nitrate NO3-1 Add Al and dil NaOH

Summary of results(2)

Name of ion Formula Test Result

Carbonate CO32- Dilute HCl followed by BaCl2 White ppt of

BaCO3 formed and gas evolved

Hydrogen carbonate

HCO3-1 Dilute HCl followed by BaCl2 Gas evolved

No ppt.

Nitrate NO3-1 Add Al and dil NaOH Gas evolved –

turns red litmus blue – alkaline gas – NH3 from the reduction of NO2

Name the Salt

• An unknown salt is dissolved in distilled water to make an aqueous solution. Sodium hydroxide is added to the solution and a green precipitate is formed that dissolves in sodium hydroxide to form a dark green solution.

• When HCl is added to the solid a gas is evolved. When barium chloride is added to the solution a white ppt is formed

• Name the salt• Write the chemical formula for this chemical

Chromium (III) Carbonate

Cr2(CO3)3