Question

Problem 10 A 1.0 L solution of MgF2 was electrolyzed for 11.8 h to give 33.02 g of magnesium. Assuming the minimum voltage needed was available, what amperage would be needed to complete the electrolysis in the given time?

Answer 1

Electrolysis equation is:
Mg2+   +   2e-    ------> Mg

1 mol of Mg requires 2 mol of electron
1 mol of electron = 96485 C
So,1 mol of Mg requires 192970 C

use:
number of mol, n = mass/molar mass
= 33.02/24.31
= 1.358 mol


total charge = mol of element deposited * charge required for 1 mol
= 1.358*1.93*10^5
= 2.621*10^5 C
t = 11.8 hr = 11.8*3600 s = 4.248*10^4 s

time, t = 4.248*10^4s

use:
i = Q/t
= 2.621*10^5/4.248*10^4
= 6.17 A
Answer: 6.17 A