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When ammonia gas is passed through an alkaline solution of potassium tetraiodomercurate(II), a precipitate is formed. The colour and the chemical formula of this precipitate are respectively:

Options

  1. ABrown, HgI ₂
  2. BYellow, HgO Hg ( NH ₂) I
  3. CWhite, Hg ( NH ₂) Cl
  4. DBrown, HgO Hg ( NH ₂) I

Correct answer

D. Brown, HgO Hg ( NH ₂) I

Step-by-step solution

An alkaline solution of potassium tetraiodomercurate(II) ( K ₂[ HgI ₄] + KOH ) is known as Nessler's reagent. When ammonia gas is passed through Nessler's reagent, it reacts to form a brown precipitate of the iodide of Millon's base. The chemical reaction is given by: 2 K ₂[ HgI ₄] + NH ₃ + 3 KOH HgO Hg ( NH ₂) I + 7 KI + 2 H ₂ O Thus, the precipitate is brown in colour and its chemical formula is HgO Hg ( NH ₂) I . Answer: Brown, HgO Hg ( NH ₂) I

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