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Analysis of Zinc Hydroxide (Zn(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: Insoluble 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 (Zn²⁺)

ExperimentObservationInference
Original solution + H₂S gas in presence of NH₄OHWhite precipitate is formedGroup IV cation may be present
Confirmatory Tests
Sodium Hydroxide Test
Add sodium hydroxide solution dropwise		White precipitate forms and dissolves in excess NaOH on heatingZn²⁺ is confirmed
Potassium Ferrocyanide Test
After neutralisation with NH₄OH, add potassium ferrocyanide solution		Bluish-white precipitateZn²⁺ is confirmed

Result

The given salt contains Zn²⁺ as the cation (basic radical) and OH⁻ as the anion (acidic radical). The salt is Zinc Hydroxide (Zn(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.

Related salts