A salt with few drops of conc. HCl gives apple green colour in flame test. The group precipitate of the salt is dissolved in acetic acid and treated with K2CrO4 to give yellow precipitate. When the sodium carbonate extract of the salt solution is heated with conc. HNO3 and ammonium molybdate, it resulted a canary yellow precipitate. The cation and anion present in the salt are respectively,
- Ca2+ and SO42-
- Ba2+ and PO43-
- Mn2+ and PO43-
- Ba2+ and SO42-
Answer
(2) Ba2+ and PO43-
Solution
Apple green flame (with conc. HCl) ⇒ Ba2+ (Ca gives brick red, Mn no characteristic flame).
Group V precipitate BaCO3 dissolves in acetic acid; with K2CrO4:
Ba2+ + CrO42- BaCrO4 (yellow) ⇒ confirms Ba2+
Sodium carbonate extract + conc. HNO3 + ammonium molybdate, heated ⇒ canary yellow precipitate of ammonium phosphomolybdate:
PO43- + 3NH4+ + 12MoO42- + 24H+ (NH4)3PO4 12MoO3 + 12H2O ⇒ PO43-
∴ Cation Ba2+ and anion PO43-
Answer: (2)