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Analysis of Potassium Fluoride (KF)

Qualitative analysis

Aim

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

Preliminary Test

  • Colour: White
  • Odour: Odourless
  • 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 (K⁺)

ExperimentObservationInference
Flame test in a clean non-luminous flameLilac flameK⁺ may be present
Confirmatory Test
Sodium Cobaltinitrite Test
Salt solution + sodium cobaltinitrite reagent
Yellow precipitateK⁺ is confirmed

Result

The given salt contains K⁺ as the cation (basic radical) and F⁻ as the anion (acidic radical). The salt is Potassium Fluoride (KF).

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.