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2 2. It is observed that a solid mixture of chloride salt and potassium dichromate is heated with con.H 2 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. a) What is significance of the sequence of reactions? b) What is the name and formula of the red vapours? c) Why red vapours are changed to yellow solution? And write its formula d) What is the yellow precipitate formed in the last step and its formula? e) Write the related chemical equations for above chemical changes.

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2.     It is observed that a solid mixture of chloride salt and potassium dichromate is heated with con.H2SO4 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.        


        a)  What is significance of the sequence of reactions?


        b)  What is the name and formula of the red vapours?


        c)  Why red vapours are changed to yellow solution?  And write its formula


        d)  What is the yellow precipitate formed in the last step and its formula?


        e)  Write the related chemical equations for above chemical changes.

Grade:Upto college level

1 Answers

Bharani VLSVSS
19 Points
13 years ago

Ans.

a) The above reactions refer to chromyl chloride test for the detection of the presence of chloride ion.

b) The name of the red vapours is CHROMYL CHLORIDE and their formula is CrO2Cl2.

c) On passing chromyl chloride through caustic soda, sodium chromate is formed which is yellow in colour.

Its formula is Na2CrO4.

d) The yellow precipitate is Lead chromate. Its formula is PbCrO4.

e) KCl + K2Cr2O7 + H2SO4 -->CrO2Cl2 + K2SO4

CrO2Cl2 + NaOH --> Na2CrO4 + H2O

Na2CrO4 + Pb(CH3COO)2 --> PbCrO4 + CH3COONa

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