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KCET2019Chemistryd and f Block Elements

A mixture of ( NaCl ) and ( K ₂ Cr ₂ O ₇ ) is heated with conc. ( H ₂ SO ₄ ), deep red vapours and formed. Which of the following statement is false?

Options

  1. AThe vapours contain ( CrO ₂ Cl ₂ ) and ( Cl ₂ )
  2. BThe vapours when passed into lead acetate in acetic acid gives a yellow precipitate.
  3. CThe vapours give a yellow solution with ( NaOH ).
  4. DThe vapours contain ( CrO ₂ Cl ₂ ) only.

Correct answer

A. The vapours contain ( CrO ₂ Cl ₂ ) and ( Cl ₂ )

Step-by-step solution

(A) Chromyl chloride test: ( 4 Cl ⁻(s)+ Cr ₂ O ₇ ²⁻(s)+6 H ⁺( )conc. ( ) 2 CrO ₂ Cl ₂ ) ( deep red vapours ) ( +3 H ₂ O ) When deep red vapours are passed into sodium hydroxide solution, a yellow solution of sodium chromate is formed, which when treated with lead acetate gives yellow precipitate of lead chromate. ( CrO ₂ Cl ₂+4 OH ⁻ CrO ₄ ²⁻+2 Cl ⁻+2 H ₂ O ) ( CrO ₄ ²⁻+ Pb ⁺² PbCrO ₄ ) ( yellow)

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