Electrochemistry 1 Question 49
48. How long a current of $3 \mathrm{~A}$ has to be passed through a solution of silver nitrate to coat a metal surface of $80 \mathrm{~cm}^{2}$ with a $0.005 \mathrm{~mm}$ thick layer?
Density of silver is $10.5 \mathrm{~g} / \mathrm{cm}^{3}$.
$(1985,3 \mathrm{M})$
Show Answer
Answer:
Correct Answer: 48. $(125 \mathrm{~s})$
Solution:
- Volume of Ag coating $=80 \mathrm{~cm}^{2} \times \frac{0.005}{10} \mathrm{~cm}=0.04 \mathrm{~cm}^{3}$
$\Rightarrow$ mass of Ag coating $=0.04 \times 10.5 \mathrm{~g}=0.42 \mathrm{~g}$
$\Rightarrow$ gram equivalent of $\mathrm{Ag}=\frac{0.42}{108}=$ number of Faraday’s
$\Rightarrow \quad \frac{0.42}{108} \times 96500 \mathrm{C}=3 \times t \Rightarrow t=125 \mathrm{~s}$
