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Analysis of Calcium Hydroxide (Ca(OH)₂)

Qualitative analysis

How to do salt analysis · Viva · Quiz

Aim

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

Preliminary Test

  • Colour: White
  • Odour: Odourless
  • State: Crystalline solid
  • Solubility: Sparingly soluble in water

Test of Anion (OH⁻)

ExperimentObservationInference
Universal IndicatorSolution turns blue or purpleOH⁻ may be present
Confirmatory Test
Phenolphthalein Test
Add phenolphthalein indicator to salt solution		Solution turns pinkOH⁻ is confirmed

Test of Cation (Ca²⁺)

ExperimentObservationInference
Original solution + Dilute HClNo reactionGroup I cation is absent
Original solution + Dilute HCl + H₂S gas (with NH₄Cl)No reactionGroup II cation is absent
Original solution + Dilute HCl + NH₄Cl solid + NH₄OHNo reactionGroup III cation is absent
Original solution + NH₄Cl + NH₄OH + (NH₄)₂CO₃White precipitate is formedGroup V cation may be present
Confirmatory Tests
Flame Test
Moisten the salt with conc. HCl and introduce it into a non-luminous flame		Brick-red flameCa²⁺ is confirmed
Ammonium Oxalate Test
Dissolve white precipitate in dilute acetic acid and add ammonium oxalate solution		White precipitate of calcium oxalateCa²⁺ is confirmed

Result

The given salt contains Ca²⁺ as the cation (basic radical) and OH⁻ as the anion (acidic radical). The salt is Calcium Hydroxide (Ca(OH)₂).

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.

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