The leaves of the rhubarb plant contain high concentrations of diprotic oxalic acid (hooccooh) and must be removed before the stems are used to make rhubarb pie. if pka1 = 1.23 and pka2 = 4.19, what is the ph of a 0.0269 m solution of oxalic acid?

Question

Chemistry

Jaiden Flynn

22 November, 07:35

The leaves of the rhubarb plant contain high concentrations of diprotic oxalic acid (hooccooh) and must be removed before the stems are used to make rhubarb pie. if pka1 = 1.23 and pka2 = 4.19, what is the ph of a 0.0269 m solution of oxalic acid?

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Larissa Hodge · Answer 1

Chemical reaction (dissociation) 1: C₂O₄H₂ (aq) ⇄ C₂O₄H⁻ (aq) + H⁺ (aq).

Chemical reaction (dissociation) 2: C₂O₄H⁻ (aq) ⇄ C₂O₄²⁻ (aq) + H⁺ (aq).

c (C₂O₄H⁻) = c (H⁺) = x.

c (C₂O₄H₂) = 0.0269 M.

pKa₁ = 1.23.

Ka₁ = 10∧ (-1.23) = 0.059.

Ka₁ = c (C₂O₄H⁻) · c (H⁺) / c (C₂O₄H₂).

0.059 = x² / (0.0269 M - x).

Solve quadratic eqaution: x = c (H⁺) = 0.02 M.

pH = - log (0.02 M) = 1.7.