Compound T contains ammonium and sulfate ions

Steps:

• Heating with NaOH produces ammonia gas (turns litmus blue), confirming NH4+ ions.
• BaCl2 test yields white precipitate insoluble in HCl, confirming SO4^2- ions (BaSO4 is acid-insoluble).
• Only a compound with both NH4+ and SO4^2- fits both observations.
• Thus, T is ammonium sulfate, (NH4)2SO4.

Why B is correct:

• Ammonium sulfate releases NH3 with NaOH/heat and forms insoluble BaSO4 with BaCl2.

Why the others are wrong:

• A: Ammonium carbonate forms BaCO3, which dissolves in HCl.
• C: Sodium carbonate lacks NH4+, so no ammonia gas.
• D: Sodium sulfate lacks NH4+, so no ammonia gas.

Final answer: B