Neco 2023 Chemistry Question 32

A white crystalline solid is dissolved in water to give a clear solution. The following observations are recorded:\n\n(a) A flame test of the solid gives a blue‑green flame.\n(b) Adding dilute HNO₃ followed by AgNO₃ produces a white precipitate that dissolves on addition of dilute NH₃ solution.\n(c) Adding NaOH to a fresh portion of the solution yields a pale blue precipitate which dissolves on addition of excess NaOH, forming a deep blue solution.\n(d) Adding NH₄OH to another portion of the solution also gives a deep blue solution.\n(e) Adding BaCl₂ to a separate portion of the solution produces no precipitate.\n(f) Passing H₂S gas through an acidic solution of the salt gives no precipitate.\nIdentify the cation and the anion present in the salt.