testing and identifying anions
DESCRIPTION
A-level chemistryTRANSCRIPT
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