Thermal decomposition yields NH3, reacting with Cl2 to identify products Steps:

• Heating Ca(OH)₂ and NH₄Cl produces NH₃ and H₂O gases via Ca(OH)₂ + 2NH₄Cl → CaCl₂ + 2NH₃ + 2H₂O.
• Passing gases through solid CaO absorbs H₂O (CaO + H₂O → Ca(OH)₂), so W = NH₃.
• NH₃ (W) reacts with Cl₂ (V) to give N₂ (X, elemental gas) and HCl (Y, acidic gas): 2NH₃ + 3Cl₂ → N₂ + 6HCl.
• HCl (Y) reacts with NH₃ (W) to form NH₄Cl (Z): NH₃ + HCl → NH₄Cl. Why B is correct:
• Z = NH₄Cl matches the product of acidic Y (HCl) reacting with basic W (NH₃), per acid-base neutralization. Why the others are wrong:
• A: Z = CaCl₂ incorrect; Y (HCl) reacts with NH₃, not to form CaCl₂.
• C: X = O₂ incorrect; reaction produces N₂, not O₂, with no oxygen source.
• D: X = O₂ and Z = NH₄Cl inconsistent; X must be N₂ from the Cl₂ reaction.

Final answer: B