PKa Inorganic Acid Base Hydrated Metal Ion Monoprotic Diprotic Triprotic Tetraprotic

Reference data and engineering information about pka inorganic acid base hydrated metal ion monoprotic diprotic triprotic tetraprotic for material properties applications.

pKainorganicacidbase

Overview

Engineering reference data for PKa Inorganic Acid Base Hydrated Metal Ion Monoprotic Diprotic Triprotic Tetraprotic in material science and properties.

Key Formulas

Stress

$\sigma = \frac{F}{A}$

Force per unit area.

Strain

$\varepsilon = \frac{\Delta L}{L_0}$

Change in length per original length.

Hooke's Law

$\sigma = E \varepsilon$

Stress proportional to strain in elastic region.

Thermal Expansion

$\Delta L = \alpha L_0 \Delta T$

Length change due to temperature.

Variables

Symbol	Description	Unit
$\sigma$	Stress	Pa
$\varepsilon$	Strain	—
$E$	Young's modulus	Pa
$\alpha$	Thermal expansion coefficient	1/°C
$\Delta T$	Temperature change	°C

DataTable: Inorganic Acid & Base pKa Values

8 rows

Selected pKₐ values for inorganic acids, bases, and hydrated metal ions. Values are measured at 25°C unless noted. For bases (marked with *), the pKₐ is for the conjugate acid BH⁺.
Acid / Base Name	Formula	pKₐ₁	pKₐ₂	pKₐ₃
Ammonia	NH₃	9.24
Arsenious acid	H₃AsO₃	9.29
Boric acid	H₃BO₃	9.24
Carbonic acid	H₂CO₃	6.35	10.33
Phosphoric acid	H₃PO₄	2.16	7.21	12.32
Sulfuric acid	H₂SO₄	-3	1.99
Aluminium(III) ion	Al³⁺	4.85
Iron(III) ion	Fe³⁺	2.17

Source: engineeringtoolbox.com

Important Definitions & Formulas

The acid dissociation constant (Kₐ) quantifies acid strength in solution. For the generic dissociation:

$\text{HA} + \text{H}_2\text{O} \rightleftharpoons \text{A}^- + \text{H}_3\text{O}^+$

The simplified expression, where the concentration of water is treated as constant, is:

$K_a = \frac{[\text{A}^-][\text{H}^+]}{[\text{HA}]}$

The pKₐ is the negative base-10 logarithm of Kₐ:

$\text{p}K_a = -\log_{10}(K_a)$

A key relationship connects pH, pKₐ, and the ratio of conjugate base to acid:

$\text{pH} = \text{p}K_a + \log_{10}\left(\frac{[\text{A}^-]}{[\text{HA}]}\right)$

Key Insights:

A larger pKₐ indicates a weaker acid (less dissociation).
When $\text{pH} = \text{p}K_a$ , the solution contains equal concentrations of the acid and its conjugate base ( $[\text{A}^-] = [\text{HA}]$ ).
Polyprotic acids (e.g., H₃PO₄, H₂CO₄) have multiple dissociation steps and corresponding pKₐ values (pKₐ₁, pKₐ₂, ...).
For a base (B), the dissociation of its conjugate acid (BH⁺) is described: $\text{BH}^+ \rightleftharpoons \text{B} + \text{H}^+$ . The pKₐ for this reaction is listed in the table (marked with *).