In an electrolytic cell, a current of 0.250 ampere is passed through a solution

Question

In an electrolytic cell, a current of 0.250 ampere is passed through a solution of a chloride of iron, producing Fe(s) and Cl_2 (g). Write the equation for the reaction that occurs at the anode. When the cell operates for 2.00 hours. 0.521 gram of iron is deposited at one electrode. Determine the formula of the chloride of iron in tire original solution. Write the balanced equation for the overall reaction that occurs in the cell. Calculate the current that would produce chlorine gas at a rate of 3.00 grams per hour.

Explanation / Answer

we know that

oxidation takes place at anode

a)

so

the equation at anode is

2Cl- ---> Cl2 + 2e-

b)

we know that

according to faradays first law of electrolysis

amount of metal deposited is given by

m = I x t x M / F x z

given

current (I) = 0.25

time (t) = 2 hrs = 2 x 60 x 60 = 7200 s

molar mass of iron = 55.845

F = faradays constant = 96485

so

0.521 = 0.25 x 7200 x 55.845 / 96485 x z

z = 2

so

two electrons are transferred

so

the individual cell reactions are

2Cl- ---> Cl2 + 2e-

Fe+2 + 2e- --> Fe

so

the formula is FeCl2

c)

the overall cell reaction is

Fe+2 + 2Cl- ---> Fe (s) + Cl2 (g)

d)

we know that

m = I x t x M / F x z

I = m x F x z / t x M

given

m = 3

t = 1 hr = 3600 s

F = 96485

z = 2

M = 71

so

I = 3 x 96485 x 2 / 3600 x 71

I = 2.265

so

2.265 ampere current is required

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