Answer:
544.522 Hours
Explanation:
a) Mass = 12.5 kg = 12500 g
Now, Number of moles is given as
No of moles = Mass of Cr / Molar mass of Cr
[tex]=\frac{12500}{52}[/tex]
= 240.38 moles
[tex]Cr^{3+}\Rightarrow[/tex] 3 mols of electrons are required
[tex]\Rightarrow 240.38\times3 =721.14\text{mol of e-}[/tex]
Converting moles of e- to coulombs of charge, (1 mol of electrons = 96500 C )
Q =721.14 mol×96500 C/mol
=69590010 of charge
We know that, Q = I×t
where Q is charge, I is current and t is time required.
[tex]\Rightarrow t =\frac{Q}{I}[/tex]
[tex]=\frac{69590010}{35.5}[/tex]
=196281.97 seconds
[tex]=\frac{1.96281\times10^5}{3600}[/tex]
=544.522 Hours
