1.

Explain about chromyl chloride test.

Answer»

Solution :(i). When potassium dichromate is heated with any chloride SALT in the presence of Conc.`H_(2)SO_(4)`, orange RED vapours of chromyl chloride (`CrO_(2)CI_(2)`) is evolved. This reaction is used to confirm the presence of chloride ION in inorganic qualitative analysis.
`K_(2)C_(2)O_(7)+ 4NaCI+ 6H_(2)SO_(4) to 2KHSO_(4)+ 4NaHSO_(4)+ underset("chromyl chloride")(2CrO_(2)CI_(2)uarr) + H_(2)O`
(II) The chromyl chloride vapours are dissolved in sodium hydroxide solution and then acidified with acetic acid and TREATED with lead acetate. A yellow precipitate of lead chromate is obtained.
`CrO_(2)CI_(2)+ 4NaOH to Na_(2)CrO_(4)+ 2NaCI+ 2H_(2)O`
`underset("Sodium chromate")(Na_(2)CrO_(4))+ underset("Lead acetate")((CH_(3)COO)_(2)Pb)to underset(underset("(Yellow precipitate)")("Lead chromate"))(PbCrO_(4)darr)+ underset("Sodium acetate")(2CH_(3)COONa)`


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