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Analysis of Ammonium Fluoride (NH₄F)

Qualitative analysis

Aim

To analyse the given inorganic salt for one acidic and one basic radical.

Preliminary Test

  • Colour: White
  • Odour: Ammoniacal
  • State: Crystalline solid
  • Solubility: Soluble in water

Test of Anion (F⁻)

ExperimentObservationInference
Take the salt and treat with concentrated H₂SO₄Colourless gas evolves and it etches glassF⁻ may be present
Confirmatory Test
Calcium Chloride Test
Treat salt solution with calcium chloride solution
White gelatinous precipitate formsPresence of F⁻ is confirmed

Test of Cation (NH₄⁺)

ExperimentObservationInference
Take 0.1 g of salt and add 1–2 mL of NaOH solution, then heatA smell of ammonia is evolvedNH₄⁺ may be present
Bring a glass rod dipped in hydrochloric acid near the mouth of the test tubeDense white fumes are observedNH₄⁺ may be present
Confirmatory Test
Nessler's Reagent Test
Pass the evolved gas through Nessler’s reagent
Brown colouration or a brown precipitate of basic mercury(II) amido-iodide is obtainedPresence of NH₄⁺ is confirmed

Result

The given salt contains NH₄⁺ as the cation (basic radical) and F⁻ as the anion (acidic radical). The salt is Ammonium Fluoride (NH₄F).

Precautions

  1. Handle the chemicals with care.
  2. Don't use excess of chemicals.
  3. Keep the mouth of the test tube away from the face.