Resposta: b) CaO, K₂CrO₄ e H₂
I - CaCO₃ → CaO + CO2
1Ca, 1C, 3O → 1Ca, 1C, 3O = Balanceada.
II - BaCℓ₂ + K₂CrO₄ → BaCrO₄ + 2 KCℓ
1Ba, 2Cl, 2K, 1Cr, 4O → 1Ba, 2Cl, 2K, 1Cr, 4O = Balanceada.
III - Zn + 2 HCℓ → ZnCℓ₂ + H₂
1Zn, 2H, 2Cl → 1Zn, 2H, 2Cl = Balanceada.