When HCl is added to an aqueous cobalt(II) solution, the equilibrium [Co(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇌ [CoCl₄]²⁻(aq) + 6H₂O(l) shifts toward the blue complex at room temperature; on cooling it becomes pink. What is the sign of ΔH for the forward reaction?
- AΔH > 0
- BΔH < 0
- CΔH = 0
- DCannot be predicted
✓ Correct answer: A
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