Question

A salt with few drops of HCl gives apple green colour on flame test. The group precipitate of the salt if dissolved in acetic acid and treated with \(K_2CrO_4\) gives yellow precipitate. When the sodium carbonate extract of the salt solution is heated with conc. \(HNO_3\) and ammonium molybdate, it results in a canary yellow precipitate. The cation and anion present in the salt are respectively:

• A. \(Ca^{2+}\) and \(SO_4^{2-}\)
• B. \(Ba^{2+}\) and \(PO_4^{3-}\)
• C. \(Mn^{2+}\) and \(PO_4^{3-}\)
• D. \(Ba^{2+}\) and \(SO_4^{2-}\)

Answer 1

The Correct Option is B

Concept: Qualitative analysis uses flame tests and confirmatory tests to identify ions.
Step 1:Identify cation} Apple green flame colour indicates: \[ Ba^{2+} \]
Step 2:Confirm cation} Reaction with \(K_2CrO_4\): \[ Ba^{2+} + CrO_4^{2-} \rightarrow BaCrO_4 \] which forms a yellow precipitate. Thus cation = \(Ba^{2+}\).
Step 3:Identify anion} Heating sodium carbonate extract with conc. \(HNO_3\) and ammonium molybdate gives a canary yellow precipitate. This confirms presence of phosphate: \[ PO_4^{3-} \] \[ \boxed{Ba^{2+} \text{ and } PO_4^{3-}} \]