Problem 5.2: Write the full carbonate equilibrium
From Chapter 5 Problem Set. Level 1: Conceptual Mastery.
Question
Write the full carbonate equilibrium expression. In one sentence, which species dominates at low, neutral, and high pH.
Answer
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CO₂(g) ⇌ CO₂(aq) ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺ ⇌ CO₃²⁻ + 2H⁺. pH determines which species dominates: low pH favors CO₂/carbonic acid, neutral pH favors bicarbonate, and high pH favors carbonate.