H3aso4 ionisasi

General
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h3aso4 ionisasi

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H3AsO4 Ionization

Answer:
Arsenic acid, chemically represented as H₃AsO₄, is a triprotic acid capable of donating three protons (H⁺ ions) in an aqueous solution. Each ionization step is associated with a specific dissociation constant (pKₐ). Below is an overview of the stepwise ionization reactions and typical pKₐ values:

  1. First Ionization:
    H₃AsO₄ → H⁺ + H₂AsO₄⁻
    pKₐ₁ ≈ 2.2

  2. Second Ionization:
    H₂AsO₄⁻ → H⁺ + HAsO₄²⁻
    pKₐ₂ ≈ 6.9–7.0

  3. Third Ionization:
    HAsO₄²⁻ → H⁺ + AsO₄³⁻
    pKₐ₃ ≈ 11.5

These reactions show that H₃AsO₄ progressively loses protons in solution, forming different ionic species depending on the pH. Each step becomes less favorable (requires a higher pH) because removing a proton from an increasingly negative species is more difficult.

Below is a summary table highlighting the ionization steps and corresponding pKₐ values:

Ionization Step Chemical Equation pKₐ
1st Ionization H₃AsO₄ → H⁺ + H₂AsO₄⁻ 2.2
2nd Ionization H₂AsO₄⁻ → H⁺ + HAsO₄²⁻ 6.9–7.0
3rd Ionization HAsO₄²⁻ → H⁺ + AsO₄³⁻ 11.5

The specific values for pKₐ can vary slightly depending on the source, temperature, and ionic strength of the solution, but the above approximations are widely accepted.

@LectureNotes