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 Answer: Option A
Explanation
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