118 8cm2 surface of the copper cathode of a vol... - JAMB Physics 2007 Question
118.8cm2 surface of the copper cathode of a voltameter is to be coated with 10-6m thick copper of density 9 x 103kgm-3. How long will the process run with 10A constant current?
[3.3 x 10-7kgC-1]
[3.3 x 10-7kgC-1]
A
5.4 min
B
10.8 min
C
15.0 min
D
20.0 min
correct option: a
From faradays law, M = itz
But mass, M = volume x density
and volume = cross sectional area x thickness
M = 118.8cm2 x 10-6 x 9 x 103
∴ 118.8cm2 x 10-6 x 9 x 103 = 10 x t x 3.3 x 10-7
∴ (118.8 x 9) x 10-7 = 10 x t x 3.3 x 10-7
∴ t = (\frac{118.8 \times 9}{ 3.3})
t = 324 seconds
Convert to minutes by dividing by 60
t = (\frac{324}{60})
t = 5.4 sec
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