Ion Tests Flashcards
Test for carbonate ions
Add aqueous acid
Positive result for carbonate ions
CO2 formed
Bubble through limewater
Limewater turns cloudy
Equation for bubbling CO2 through limewater
CO2 + Ca(OH)2 —> CaCO3 (precipitate) + H2O
Test for sulfate ions
Acidify with dilute HCl
Add barium chloride
Positive result for sulfate ions
White precipitate forms
Equation for test for sulfate ions
Ba2+ + SO42- —> Ba2+SO42-
Test for ammonium ions
Add NaOH
Warm mixture
Test gas with damp litmus
red litmus paper turns blue
Positive result for ammonium ions
Litmus paper goes from red to blue
Equation for ammonium test
NH4+ + OH- —> NH3 + H2O
Test 1 for halide ions
Add dilute HNO3 (to remove impurities)
Add silver nitrate
Results for test 1 for halide ions
Cl- white precipitate
Br- cream precipitate
I- yellow precipitate
Test 2 for halide ions
Add dilute NH3
Results for test 2 for halide ions
Cl- dissolves
Br- remains
I- remains
Test 3 for halide ions
Add concentrated NH3
Result for test 3 of halide ions
Cl- dissolves
Br - dissolves
I- remains
Test for cations
Add ammonia/NaOH
Results for cations
Cu2+ blue Fe2+ green Cr3+ green (in excess NH3 will turn purple) Fe3+ brown Mn3+ brown/pink
How would you confirm that no other halide ions are present
Add dilute NH3 and precipitate completely dissolves
