Chemistry / Unit 10 Chem 1818 short lesson, about 20 seconds
Autoionization of Water and Kw
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The idea
Water reacts with itself, H2O + H2O ⇌ H3O+ + OH−, giving Kw = [H3O+][OH−]; at 25 °C this defining value is 1.0 × 10⁻¹⁴.
In practice
In pure water at 25 °C, [H3O+] and [OH−] each equal 1.0 × 10⁻⁷ M, satisfying Kw.
Where people slip
Kw holds in any aqueous solution at a given temperature, acidic or basic, not only pure water.
Your place on the trail
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