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Experiment No. N

Analysis of Manganese(II) Nitrite (Mn(NO₂)₂)

Aim

To determine the presence of anion and cation in the given salt

Preliminary Test

  • Odor: Odorless
  • Texture: Crystalline
  • Color: White
  • Solubility: Soluble in water

Test of Anion

ExperimentObservationInference
Warm the solid salt with dilute H₂SO₄Brown fumes of NO₂ are evolvedNO₂⁻ may be present
Confirmatory Tests
Potassium Iodide Starch Test
Take evolved gas and add KI + starch solution acidified with acetic acid		Blue colour appearsNO₂⁻ is confirmed
Sulphanilic Acid / 1-Naphthylamine Test
Acidify 1 mL of water extract with acetic acid and add sulphanilic acid solution followed by 1-naphthylamine reagent		Red colour is formedNO₂⁻ is confirmed

Test of Cation

ExperimentObservationInference
Original solution + H₂S gas in presence of NH₄OHBlack or flesh-coloured precipitate is formedGroup IV cation may be present
Confirmatory Test
Sodium Hydroxide Test
Dissolve the precipitate in dilute HCl by boiling and add NaOH in excess		White precipitate forms first, then turns brown on standingPresence of Mn²⁺ is confirmed

Result

The given salt contains Mn²⁺ ions as cation and NO₂⁻ ions as anion. The salt is Mn(NO₂)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.