Determine the ph of a 0.18 m h2co3 solution. carbonic acid is a diprotic acid whose ka1 = 4.3 * 10-7 and ka2 = 5.6 * 10-11. determine the ph of a 0.18 m h2co3 solution. carbonic acid is a diprotic acid whose ka1 = 4.3 * 10-7 and ka2 = 5.6 * 10-11. 4.31 5.50 11.00 10.44 3.56

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Chemistry

Ximena Reynolds

23 September, 22:05

Determine the ph of a 0.18 m h2co3 solution. carbonic acid is a diprotic acid whose ka1 = 4.3 * 10-7 and ka2 = 5.6 * 10-11. determine the ph of a 0.18 m h2co3 solution. carbonic acid is a diprotic acid whose ka1 = 4.3 * 10-7 and ka2 = 5.6 * 10-11. 4.31 5.50 11.00 10.44 3.56

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Bernard Lang · Answer 1

Answer is: ph value is 3.56.

Chemical reaction 1: H₂CO₃ (aq) ⇄ HCO₃⁻ (aq) + H⁺ (aq); Ka₁ = 4,3·10⁻⁷.

Chemical reaction 2: HCO₃⁻ (aq) ⇄ CO₃²⁻ (aq) + H⁺ (aq); Ka₂ = 5,6·10⁻¹¹.

c (H₂CO₃) = 0,18 M.

[HCO₃⁻] = [H⁺ ] = x.

[H₂CO₃] = 0,18 M - x.

Ka₁ = [HCO₃⁻] · [H⁺] / [H₂CO₃].

4,3·10⁻⁷ = x² / (0,18 M - x).

Solve quadratic equation: x = [H⁺] = 0,000293 M.

pH = - log[H⁺] = - log (0,000293 M).

pH = 3,56; second Ka do not contributes pH value a lot.