Testing for Ions

Question 1

How can you generally test for group 2 metal ions? What does a positive test look like?

Answer 1

• Test Tube reaction
• Add Group 2 CHLORIDES to 4 separate tubes
• Add (Excess NaOH, Ammonia solution, Excess H2SO4) dropwise

Question 2

Test for Ammonium Ions?

Answer 2

• NaOH added to ammonium (chloride)
• Swirl, mix
• Place test tube in warm water bath
• Fumes produced
• Use tongs to hold damp RED litmus paper to mouth of test tube
• Turns blue if ammonia gas present

Question 3

Testing for Halide Ions?

Answer 3

If necessary, adding ammonium : AgCl and AgBr form soluble complex, colourless, AgI forms INSOLUBLE complex, remains yellow

Question 4

Testing for Hydroxide Ions (OH)

Answer 4

• Red litmus paper turns blue
• Universal Indicator indicates alkaline solution

Question 5

Testing for Carbonate Ions

Answer 5

• Add dilute HCL
• CO2 gas should be observed

(Can deliver limewater (Ca(OH2)) solution into the test tube via a tube which would turn the test tube solution cloudy because calcium carbonate forms in the presence of CO2)

Question 6

Testing for Sulphate ions

Answer 6

• Add dilute HCL
• Add BaCl
• BaSO4 forms (white precipitate)