Redox, electrolysis, 3 (Redox-53) 15 m2 a metal surface area should with a 35 µm thick chromic layer coated are. Chromes has a density of 7.15 g/cm3. (a) Calculate the mass of chromium to be excreted. (b) Separation shall be made from an CrO3 – solution. How long to be electrolyzed if the current strength is 450 A And the effectiveness is 90%. Note : identical exercise also at the same time, subjects salts.

  Exercise: Redox-53    

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15 m² a metal surface area should with a 35 µm thick chromic layer coated are. Chromes has a density of 7.15 g/cm³.
(a) Calculate the mass of chromium to be excreted.
(b) Separation shall be made from an CrO₃ – solution. How long to be electrolyzed if the current strength is 450 A And the effectiveness is 90%.
Note : identical exercise also at the same time, subjects salts.

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Solution:

Note: 35 µm correspond to 35·10^-6m

1. The volume of the chromium layer to be added shall be:
       V= O·h = 15m^2·35·10-6m = 0.000525 m³ = 525 cm³
2. With density = m/V:
       m=density·V= 7.15g/cm³ · 525 cm³ = 3753.75 grams
3. CrO₃, participants ions: Cr⁶⁺/O^2-
       Cr⁶⁺ + 6e^– → Cr, z = 6
4. m/M = I·t/(z·F)
       t = m·z·F/(M·I) = 96485·6·3753/(52·450)
       t = 92848 s (at 100% efficiency)
5. Efficiency of 90%: 103164 seconds

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