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An aqueous solution containing Pb²⁺ ions reacts with K₂CrO₄ to yield a yellow precipitate (A). When precipitate (A) is treated with hot concentrated NaOH , it dissolves to form a clear solution containing a soluble complex (B). The chemical formula of the soluble complex (B) is:

Options

  1. ANa₂[Pb(CrO₄)₂]
  2. BNa₄[Pb(OH)₆]
  3. CNa₂[PbO₃]
  4. DNa₂[Pb(OH)₄]

Correct answer

D. Na₂[Pb(OH)₄]

Step-by-step solution

When potassium chromate is added to a solution containing Pb²⁺ ions, a yellow precipitate of lead chromate (A) is formed. Pb²⁺ + CrO₄²⁻ PbCrO₄ Lead is an amphoteric metal, and its salts like lead chromate dissolve in excess of strong alkalis such as sodium hydroxide. The dissolution occurs due to the formation of a soluble tetrahydroxoplumbate(II) complex (B). PbCrO₄ + 4NaOH Na₂[Pb(OH)₄] + Na₂CrO₄ Thus, the soluble complex (B) is Na₂[Pb(OH)₄] . Answer: Na₂[Pb(OH)₄]

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