When CO₂(g) is dissolved in water, the following equilibrium is established:
CO₂(aq) + 2H₂O(l) ⇌ H₃O⁺(aq) + HCO₃⁻(aq)
for which the equilibrium constant is 3.8 × 10⁻⁷. If the pH of solution is 6

Question

When CO₂(g) is dissolved in water, the following equilibrium is established:
CO₂(aq) + 2H₂O(l) ⇌ H₃O⁺(aq) + HCO₃⁻(aq)
for which the equilibrium constant is 3.8 × 10⁻⁷. If the pH of solution is 6.0, what would be the ratio of concentration of HCO₃⁻(aq) to CO₂(aq)?

Prashant Kotian · Accepted Answer

Correct answer: C. Given pH = 6.0, [H₃O⁺] = 10⁻⁶ M. The equilibrium constant K = [H₃O⁺][HCO₃⁻] / [CO₂] = 3.8 × 10⁻⁷. Substituting [H₃O⁺], we get 10⁻⁶ × ([HCO₃⁻] / [CO₂]) = 3.8 × 10⁻⁷. The ratio [HCO₃⁻] / [CO₂] = 3.8 × 10⁻⁷ / 10⁻⁶ = 0.38. Therefore, correct answer is C.

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