pH calculations, 2 (SB-48) Calculate the mass H3O+ and OH– In the … (a) … one litre of water. pH = 6 (b) … in Lake Constance. 7

  Aufgabe: SB-48    

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Calculate the mass H₃O⁺ and OH^– In the …

1. (a) … one litre of water. pH = 6
2. (b) … in Lake Constance. 7

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Lösung:

With pH = -log(c(H₃O⁺)) is replaced by the following:(H₃O⁺) = 10^-pH
It is the same.

1. With pH = -log(c(H₃O⁺)) shall read as follows:
       c(H₃O⁺) = 10^-pH and c.(OH^–) = 10^-pOH
       The same applies to c=n/V=m/M/V and thus:
       m = c·V·M
2. a) m(H₃O⁺) = c·V·M=10^-6 mol/l · 1.0 l · 19 g/mol = 1.9·10^-5 Grams
       m(OH^–) = 10^-8 mol/l · 1.0 l · 17 g/mol = 1.7·10^-7 Grams
3. (b) Constance volume, rough estimate: l= 50 km, b= 2km, h=300m
       V = 30 km³=30·(1000m·1000m·1000m)=10⁹ m³ = 10¹² Litre
       m(H₃O⁺) = c·V·M=10^-7 mol/l · 10¹² l · 0.019 kg/mol = 1900 kg
       m(OH^–) = 10^-7 mol/l · 10¹² l · 0.017 kg/mol = 1700 kg

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