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.
m(C₂O₄H₂) =
2.2507 g.
n(C₂O₄H₂) = m(C₂O₄H₂) ÷ M(C₂O₄H₂).
n(C₂O₄H₂) = 2.2507 g ÷ 90.03 g/mol.
n(C₂O₄H₂) = 0.025 mol.
V(C₂O₄H₂) = 250.0 mL = 0.25 L.
c(C₂O₄H₂) = 0.025 mol / 0.25 L = 0.1M.
Ka₁ = 6.5·10⁻².
Ka₁ =
c(C₂O₄H⁻) ·
c(H⁺) / c(C₂O₄H₂).
0.065 = x² / (0.1 M - x).
Solve quadratic eqaution: x = c(H⁺) = 0.0544 M.
pH(oxalic acid) = -log(0.0544 M) = 1.26.
