Salts, electrolysis, 7 (Salze-91) Calculate the thickness of the copper layer that a current of 5.8 A dissolves evenly in 3 hours on a sphere with a radius of 8.3 cm. Note 1: The surface of a sphere is 4·pi·r2 Note 2: Coppering was carried out with a copper sulphate solution Note 3: Dichte(Cu) = 8.9 g/cm3 Note: Identical exercise also in the subject of redox

  Exercise: Salze-91    

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Calculate the thickness of the copper layer that a current of 5.8 A dissolves evenly in 3 hours on a sphere with a radius of 8.3 cm.
Note 1: The surface of a sphere is 4·pi·r²
Note 2: Coppering was carried out with a copper sulphate solution
Note 3: Dichte(Cu) = 8.9 g/cm³
Note: Identical exercise also in the subject of redox

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Solution:

1. · Copper sulphate solution: CuSO₄, or Cu²⁺/SO2-4
2.     Cu²⁺ + 2e^– → Cu, z = 2
3. · m/M = I·t/(z·F)
4.     m = I·t·M/(z·F) = 5.8·3600·3·63.5/(2·96485) = 20.6 g
5.     Units: [A·s·g/mol/(A·s/mol)] = [g]
6. · Es of which: approximate: the volumes (!) the bullet layer is equal the surface of the sphere multiplied by with the height, or Thick (:d) the layers V = 4·π·r²·d
7. · Density = m/V
8.     m = density · V = Dichte·4·π·r²·d
9.    
10.     → d = m/(Dichte·4·π·r²)
11.     d = 20.63/(8.9·4·π·8.3²) = 2.67·10^-3cm = 0.026 mm

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