W = HCl + HNO₃. Silver nitrate → white precipitate (chloride → HCl); barium nitrate → no observable change (no sulfate); NaOH + aluminium foil, warmed → effervescence, and the gas turns damp red litmus paper blue → ammonia → nitrate → HNO₃.
X (acidified FeCl₃) + Y (KI) → iodine; starch → blue-black; thiosulfate delays it. More X → faster. Rate = 1000/time, no graph. Ratio = rate 2 ÷ rate 1.
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