7 QUALITATIVE ANALYSIS

• What is the order of tests to carry out when testing for anions?

  Tests should be carried out in the same order as in the provided table.
• How does NH3 distinguish silver halide precipitates?

  NH3 distinguishes silver halide (AgX) precipitates by their solubility in ammonia.
• What happens to silver chloride when dilute ammonia is added?

  Silver chloride dissolves in dilute ammonia.
• What happens to silver bromide when concentrated ammonia is added?

  Silver bromide dissolves in concentrated ammonia.
• What is the solubility of silver iodide in concentrated ammonia?

  Silver iodide is insoluble in concentrated ammonia.
• How can carbonates (CO3 2-) be tested?

  Add dilute acid to produce effervescence due to CO2 production.
• What is the procedure for testing sulfates (SO4 2-)?

  Add dilute HCl and BaCl2 to produce a white precipitate of BaSO4.
• How are halides (Cl-, Br-, I-) tested?

  Add HNO3 and AgNO3 to observe precipitate colors: Cl = white, Br = cream, I = yellow.
• What happens when aqueous NaOH is added to transition metal ions?

  It produces precipitates.
• How can ammonium ions be tested?

  Heat with OH- ions to produce ammonia gas.
• What is the chemical equation for the reaction of ammonium ions with hydroxide ions?

  NH4+ (aq) + OH- (aq) → NH3 (g) + H2O (l)
• What does ammonia do to damp red litmus paper?

  It turns damp red litmus paper blue, confirming the presence of ammonium ions.
• Cr 3+ colour

  violet solution
• Fe 2+ colour

  green solution
• Fe 3+ colour

  yellow solution
• Mn 2+ colour

  pale pink solution
• Cu 2+ colour

  blue solution
• Cr 3+ with OH-

  green precipitate, Cr(OH)3(H2O)3
• Fe 2+ with OH-

  green precipitate, Fe(OH)2(H2O)4
• Fe 3+ with OH-

  brown precipitate, Fe(OH)3(H2O)3
• Mn 2+ with OH-

  pale brown precipitate, Mn(OH)2(H2O)4
• Cu 2+ with OH-

  blue precipitate, Cu(OH)2(H2O)4
• Cr 3+ with excess OH-

  green solution, [Cr(OH)6]3-
• Fe 2+ with excess OH-

  no change
• Fe 3+ with excess OH-

  no change
• Mn 2+ with excess OH-

  no change
• Cu 2+ with excess OH-

  no change