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# Kw-pH - Todays lesson is brought to you by 7 14 and the...

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Today’s lesson is brought to you by Today’s lesson is brought to you by 7, 14, and the letters 7, 14, and the letters Kw, pH Kw, pH

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Kw: the ion-product constant of water Kw: the ion-product constant of water Q: will pure distilled water conduct electricity A: As the demo shows, it will (slightly). If water conducts electricity, ions must exist Water exists as an equilibrium, which is referred to as the self-ionization of water: H 2 O + H 2 O H 3 O + (aq) + OH (aq) Simplified reaction : H 2 O H + (aq) + OH (aq) Kc = [H 3 O + ] [OH ] [H 2 O] 2 Kw = or [H 3 O + ] [OH ] Note: H + is just shorthand for H 3 O + Kc = [H + ] [OH ] [H 2 O] Kw = or [H + ] [OH ]
Kw Kw What is the value of Kw? It has been measured at 1.0 x 10 –14 (25 °C) Notice (pg. 600) that by definition: when the solution is [H + ] > [OH ] acidic [H + ] < [OH ] basic [H + ] = [OH ] neutral Pure water is neutral since [H + ] and [OH ] must be identical (both come from one H 2 O) As temperature increases Kw increases Q: Rewrite the equilibrium of water with heat as a product or reactant (based on above point) Q: Do PE 1 (refer to example 15.1)

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