Question

A metal gives two chlorides ‘a' and ‘b'. ‘a' gives black precipitate with n h 4 o h and ‘b' gives white precipitate .with ki ,‘b' gives a red precipitate soluble in excess of ki. ‘a' and ‘b' are respectively :

Answer 1

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