P is a white solid (a hydrogencarbonate). Gentle heating releases CO₂ (limewater → milky) + water vapour (condensation) — the solid hardly changes, and there is no effervescence from a dry solid. With solution Q, P effervesces (CO₂ again) and a light blue precipitate settles.
Q = copper(II) chloride: Ba(NO₃)₂ → no change (no sulfate); AgNO₃ → white ppt (Cl⁻); ammonia slowly → light blue ppt, then both ppts dissolve in excess → dark blue solution (Cu²⁺); NaOH → light blue ppt insoluble in excess. P is a carbonate (CO₃²⁻).
Indicator I is green in alkali, purple in acid. Drop-count to the end-point: R₁ = 13, R₂ = 7 → R₁ ≈ twice as concentrated.
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