Question

Metallic magnesium can be made by the electrolysis of molten MgCl2.

Part A What mass of Mg is formed by passing a current of 6.00 A through molten MgCl2 for 4.60 days? m =   g Mg

Part B

How many minutes are needed to plate out 29.00 g Mg from molten MgCl2, using 4.10 A of current?

t =		min

Answer 1

A)

the electrolysis expression 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

let us calculate the charge passed:

t = 4.6 days = 4.6*24*3600 s = 397439 s

time, t = 397439s

Q = I*t

= 6A * 397439s

= 2384634 C

mol of Mg plated = 2384634/192970 = 12.35754 mol

Molar mass of Mg = 24.31 g/mol

mass of Mg = number of mol * molar mass

= 12.35754 * 24.31

= 300. g

Answer = 300. g

B)

the electrolysis expression 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

let us calculate mol of element deposited:

we have below equation to be used:

number of mol, n = mass/molar mass

= 29/24.31

= 1.19292 mol

total charge = mol of element deposited * charge required for 1 mol

= 1.19292*192970

= 230198.6837 C

we have below equation to be used:

time = Q/i

= 230198.6837/4.1

= 56146.0204 seconds

= 56146.0204/60 min

= 936 min

Answer: 936 min