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Calculate the mass at H3O+ and OH– in …
- a) … one litre of water. pH = 6
- (b)… in Lake Constance. The pH was 7
Solution: With pH = -log(c(H3O+)) following:: c(H3O+) = 10-pH
It is the same.- The pH = -log(c(H3O+)) is as follows:
c(H3O+) = 10-pH or c(OH–) = 10-pOH
Similarly, c=n/V=m/M/V and thus:
m = c·V·M - (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 - b) volumes lake Constance, coarse estimated: l= 50 km, b= 2km, h=300m
V= 30km3=30·(1000m·1000m·1000m)=109 m3 = 1012 litres
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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