Ionic product of water Kw
Ionic product of water Kw
Formula
Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ mol² dm⁻⁶ (at 25°C)
Real World
In high-pressure steam turbines at power stations like Drax, water at 200°C has a Kw much larger than 10⁻¹⁴, making pure water more acidic (lower pH) even though it is still neutral because [H⁺] = [OH⁻].
Exam Focus
State that Kw increases with temperature because dissociation is endothermic — examiners expect the Le Chatelier reasoning.
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