It is observed that a solid mixture of chloride salt and potassium dichromate is heated with con. $$\text{H}_2\text{SO}_4$$ red vapours are formed. When these vapours are passed into aqueous caustic soda solution yellow solution is formed. This on further treatment with lead acetate solution, a yellow precipitate is formed.<br>a) What is significance of the sequence of reactions?<br>b) What is the name and formula of the red vapours?<br>c) Why red vapours are changed to yellow solution? And write its formula<br>d) What is the yellow precipitate formed in the last step and its formula?<br>e) Write the related chemical equations for above chemical changes.

PLACEHOLDER ANSWER - the question has five written parts. a) It is the chromyl chloride test, which confirms the chloride ion (bromides and iodides do not give it). b) The red vapours are chromyl chloride, $$\text{CrO}_2\text{Cl}_2$$. c) Chromyl chloride reacts with NaOH to form yellow sodium chromate, $$\text{Na}_2\text{CrO}_4$$. d) The yellow precipitate is lead chromate, $$\text{PbCrO}_4$$. e) $$4\text{NaCl} + \text{K}_2\text{Cr}_2\text{O}_7 + 6\text{H}_2\text{SO}_4 \rightarrow 2\text{KHSO}_4 + 4\text{NaHSO}_4 + 2\text{CrO}_2\text{Cl}_2 + 3\text{H}_2\text{O}$$; $$\text{CrO}_2\text{Cl}_2 + 4\text{NaOH} \rightarrow \text{Na}_2\text{CrO}_4 + 2\text{NaCl} + 2\text{H}_2\text{O}$$; $$\text{Na}_2\text{CrO}_4 + (\text{CH}_3\text{COO})_2\text{Pb} \rightarrow \text{PbCrO}_4 + 2\text{CH}_3\text{COONa}$$.