When molten zinc chloride (ZnCl 2 ) is electrolyzed, zinc is deposited at the ca

Question

When molten zinc chloride (ZnCl2) is electrolyzed, zinc is deposited at the cathode. Calculate the amount of zinc produced if a current of 12.2 A is passed through the electrolytic cell for 45.3 min.

THEN

A metal bromide, MBr2, is converted to a molten form at high temperature. Electrolysis of this sample with a current of 6.23 A for 73.2 seconds results in deposition of 0.266 g of metal M at the cathode. The other product is bromine gas, Br2(g), which is released at the anode. Determine the identity of metal M.

Explanation / Answer

Question 1.

t = 45.3 min = 45.3*60 = 2718 seconds

Total charge:

I = C/t

C = I*t = (12.2)(2718) = 33159.6 C

change to mol of e-

1 mol of e- = 96500 C

x mol = 33159.6 C

x = 33159.6/96500 = 0.343622 mol of e-

note taht

1 mol of Zn = 2 mol of e- required

0.343622 mol of e- --> !/2*0.343622 = 0.171811 mol of ZN

mass = mol*Mw = 0.171811*65.38 = 11.23300 g of Zn

PART 2:

MBr2 <-> M+2 + 2Br-

total charge = 6.23*73.2 = 456.036 C

mol of e- = 456.036/96500 = 0.00472 mol of e-

mol of M+2 = 1/2*0.00472 = 0.00236 mol of M+2

MW = mass/mol = 0.266/0.00236 = 112.71 g/mol

MW of Cd = 112.1 g/mo, this must be Cadmium, Cd

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