A galvanic (voltaic) cell contains a copper cathode immersed in a copper(II) chl

Question

A galvanic (voltaic) cell contains a copper cathode immersed in a copper(II) chloride solution and a nickel anode immersed in a nickel (II) chloride solution. The two solutions are connected with a salt bridge. Write the balanced equation for the galvanic cell. Phases are optional. A current of 1.77 A is observed flowing through the cell for a period of 2.03 hours. Calculate the amount of charge flowing through the circuit during this time. Calculate the number of moles of electrons flowing through the circuit during this time. Calculate the mass change in grams of the copper and nickel electrodes.

Explanation / Answer

The equations

Ni2+ + 2 e Ni(s) 0.25

Cu2+ + 2 e Cu(s) +0.337

note that in other to occur in a forward direction, we need nickel to oxidize and copper to reduce ( due to their potentials)

Cu2+ + 2 e Cu(s) +0.337

Ni(s) Ni2+ + 2 e   0.25

Overall reaction, balanced

Cu2+(aq) + Ni(s) --> Cu(s) + Ni2+2(aq)

E° = Ered - Eox = 0.337 --0.25 = 0.587 V

so

B)

I = 1.77 A

t = 2.03 h

find total charge

Total C = I*t = (1.77 C/s)(2.03 h) = 1.77 C/s * 2.06*3600 s = 13126.32 C

C)

total mol, according to faraday:

F = 96500 C/mol

mol of e- in 13126.32 C

mol = 13126.32/96500

mol = 0.1360 mol of e-

D)

mass changes:

2 mol of e- --> 1 mol of metal

mol of metal --> 0.1360 /2 = 0.068 mol of metal

so

Cu increases, Ni decreases

0.068 mol o Cu+2 = 0.068*63.5 = 4.318 g of Cu increase

0.068 mol of Ni decrease = 0.068*58.6934 = 3.991 g of ni decreae

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