: ANA CHEM_LAB_GROUP V, IV, III CATIONS

Analysis of Group V Cations

I. Materials / Reagents

  • Sodium Nitrate (NaNO3)

  • Potassium Nitrate (KNO3)

  • Ammonium Nitrate (NH4NO3)

  • Sodium Hydroxide (NaOH)

  • 12 M Hydrochloric Acid (HCl)

  • 6 M Hydrochloric Acid (HCl)

  • Sodium Cobaltinitrite (Na3Co(NO2)6)

  • Litmus Paper

II. Apparatuses

  • Nichrome Wires

  • 2 Thickness Cobalt Glass

III. Procedures

A-1. Test for Ammonium Ion (NH4+)

  • Add 6 mL NaOH to 1 mL of solution until alkaline, then excess NaOH.

  • Moisten red litmus and cover evaporating dish with a watch glass.

  • Heat; if litmus turns blue, NH4+ is present.

    • Result: Red litmus turns blue.

    • Confirmatory Equation: NH4+ + OH- —heat→ NH3↑ + H2O

A-2. Test for Sodium Ion (Na+)

  • Acidify 1 mL solution with 12 M HCl, then perform a flame test.

  • Clean wire loop before use.

  • Compare flame color of unknown with a known solution.

    • Result: Persistent and intense yellow flame indicates Na+ presence.

    • Confirmatory Equation: NaNO3 + HCl → NaCl + HNO3

A-3. Test for Potassium Ion (K+)

  • Using cobalt glass, view flame during testing; vibrant colors confirm K+ presence.

    • Result: Reddish-violet with cobalt glass; pale violet with the naked eye.

    • Confirmatory Equation: KNO3 + HCl → KCl + HNO3

A-4. Alternative Test for Potassium Ion

  • Add sodium cobaltinitrite; yellow precipitate indicates K+.

    • Result: Yellow precipitate confirms K+ presence.

    • Chemical Equation: 2K+ + Na3Co(NO2)6 → K2NaCo(NO2)6↓ + 2Na+

Summary of Group V Cations Presence

  • Ammonium (NH4+): Red litmus turns blue.

  • Sodium (Na+): Intense yellow flame.

  • Potassium (K+): Reddish-violet flame or yellow precipitate from Na3Co(NO2)6.

Analysis of Group IV Cations

I. Materials / Reagents

  • Distilled Water

  • Magnesium Nitrate (Mg(NO3)2)

  • Barium Nitrate (Ba(NO3)2)

  • Strontium Nitrate (Sr(NO3)2)

  • Calcium Nitrate (Ca(NO3)2)

  • 5 M Ammonium Chloride (NH4Cl)

  • 15 M Ammonium Hydroxide (NH4OH)

  • 1 M Potassium Chromate (KCr2O4)

II. Apparatuses

  • Centrifuge

III. Procedures

  • Prepare solution with magnesium, barium, strontium, and calcium nitrates.

B. Precipitation of Group IV

  • Add 5 M NH4Cl and NH4OH to the unknown solution; heat and add (NH4)2CO3 for precipitation.

  • Test for exceeding precipitation and confirm magnesium or group V.

B-1. Test for Barium Ion (Ba2+)

  • Use HAc and K2CrO4; apple green flame confirms presence.

    • Result: Yellow ppt. with K2CrO4.

    • Confirmatory Equation: BaCO3 + K2CrO4 → BaCrO4↓ + K+ + CO3 2–

B-2. Test for Strontium Ion (Sr2+)

  • Use ammonium sulfate and look for white precipitate.

    • Result: Deep red flame indicates Sr2+.

B-3. Test for Calcium Ion (Ca2+)

  • Use ammonium oxalate to test; orange-red flame confirms presence.

    • Result: White ppt. confirms Ca2+.

B-4. Test for Magnesium Ion (Mg2+)

  • Add sodium phosphate, heat for blue precipitate.

    • Result: White gelatinous ppt.

    • Confirmatory Equation: Mg2+ + Na2HPO4 → MgNH4PO4 + H2O.

Summary of Group IV Cations Presence

  • Barium (Ba2+): Confirmed by yellow ppt., apple-green flame.

  • Strontium (Sr2+): Confirmed by deep red flame.

  • Calcium (Ca2+): Confirmed by white ppt., orange red flame.

  • Magnesium (Mg2+): Confirmed by a white gelatinous ppt.

Analysis of Group III Cations

I. Materials / Reagents

  • Manganese Nitrate (Mn(NO3)2)

  • Ferric Nitrate (Fe(NO3)3)

  • Cobaltous Nitrate (Co(NO3)2)

  • Nickelous Nitrate (Ni(NO3)2)

  • Aluminum Nitrate (Al(NO3)3)

II. Apparatuses

  • Centrifuge

III. Procedures

E. Precipitation of Group III Cations

  • Use ammonium chloride, thioacetamide; heat mixture.

E-1. Separation and Test for Manganese Ion (Mn2+)

  • Chemical processes yield a pink/purple color confirming manganese.

E-2. Separation and Test for Ferric Ion (Fe3+)

  • Confirm presence using KSCN; deep red solution indicates Fe3+.

E-3. Test for Cobalt Ion (Co2+)

  • Add reactions with KNO3; yellow/olive ppt. indicates Co2+.

E-4. Test for Nickel Ion (Ni2+)

  • Dimethylglyoxime gives red precipitate confirming nickel.

F-1. Test for Aluminum Ion (Al3+)

  • Confirm presence as white gelatinous precipitate; red precipitate indicates Al3+.

Summary of Group III Cations Presence

  • Manganese (Mn2+): Pink/purple color.

  • Nickel (Ni2+): Red ppt.

  • Ferric (Fe3+): Deep red color.

  • Cobalt (Co2+): Deep blue color.

  • Zinc (Zn2+): Foggy white ppt.