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]
A. 5.4 min B. 10.8 min C. 15.0 min D. 20.0 min
Correct Answer: 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
