GKFix MCQ Question

Which of the following is an example of physical equilibrium?

• A. CH3COOH ⇌ CH3COO⁻ + H⁺
• B. N2(g) + 3H2(g) ⇌ 2NH3(g)
• C. H2O(l) ⇌ H2O(vap)
• D. CaCO3(s) ⇌ CaO(s) + CO2(g)