Ionization Dissociation Autoprotolysis Constant PKw Water Heavy Deuterium Oxide

Overview

Engineering reference data for Ionization Dissociation Autoprotolysis Constant PKw Water Heavy Deuterium Oxide in chemistry.

Key Formulas

Ideal Gas Law

$PV = nRT$

Pressure × Volume = moles × gas constant × temperature.

Molarity

$M = \frac{n}{V}$

Moles of solute per liter of solution.

pH

$pH = -\log_{10}[H^+]$

Measure of acidity.

Variables

Symbol	Description	Unit
$P$	Pressure	Pa
$V$	Volume	m³
$n$	Moles	mol
$R$	Gas constant	8.314 J/(mol·K)

Heavy Water Ionization Properties

Heavy water (D₂O) self-ionizes less readily than normal water (H₂O), resulting in higher pKw values at equivalent temperatures. This difference arises from the stronger hydrogen bonding in D₂O due to the greater mass of deuterium, which affects the equilibrium:

$2\text{D}_2\text{O} \rightleftharpoons \text{D}_3\text{O}^+ + \text{OD}^-$

At 25°C:

• H₂O: pKw = 13.995 → Kw = 1.012 × 10⁻¹⁴
• D₂O: pKw = 14.951 → Kw = 1.119 × 10⁻¹⁵

Temperature-Dependent Ionization Constants

Key observations:

• pKw reaches a minimum around 250°C for H₂O, indicating maximum ionization
• At temperatures above ~250°C, pKw increases again due to reduced dielectric constant
• D₂O data are available only up to 100°C; heavy water has approximately 1 pKw unit higher than H₂O across all measured temperatures

Interactive Charts

References

• Original Source