Explain chromyl chloride Test

Explanation

(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)Cl_(2))` is evolved.
(iii) This reaction is used to confirm the presence of chloride ion in inorganic qualitative analysis .
` K_(2)Cr_(2)O_(7) + 4NaCI + 6H_(2)SO_(4) to 2KHSO_(4) + 4NaHSO_(4) underset(" Chromyl chloride " ) ( 2 CrO_(2) CI_(2))uarr + 3H_(2)O`
(iii) 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)Cl_(2) + 4NaOH to Na_(2)CrO_(4) + 2NaCI + 2H_(2)O`
` Na_(2)CrO_(4) + (CH_(3)COO)_(2) Pb to underset( " Leadchromate Yellowprecptiate") darr + 2CH_(3) COONa`