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 K_2CrO_4 to give yellow precipitate. When the sodium carbonate extract of the salt solution is heated with conc. HNO_3 and ammonium molybdate, it resulted a canary yellow precipitate. The cation and anion present in the salt are respectively,
B. Ba^ 2+ and PO_4^ 3-
An apple green colour in the flame test indicates the presence of Ba^ 2+ ion. The group precipitate of Ba^ 2+ is BaCO_3, which dissolves in acetic acid to form barium acetate. Upon treatment with K_2CrO_4, it gives a yellow precipitate of barium chromate (BaCrO_4), confirming the presence of Ba^ 2+ . When the sodium carbonate extract is heated with conc. HNO_3 and ammonium molybdate, the formation of a canary yellow precipitate indicates the presence of phosphate (PO_4^ 3- ) ion. The canary yellow precipitate is ammonium phosphomolybdate, (NH_4)_3PO_4 12MoO_3. Therefore, the cation is Ba^ 2+ and the anion is PO_4^ 3- . Answer: Ba^ 2+ and PO_4^ 3-
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