Question

A voltaic cell similar to that shown in Figure 20.5 is con-structed. One half-cell consists of an aluminum strip placed in a solution of Al1NO323, and the other has a nickel strip placed in a solution of NiSO4. The overall cell reaction is

2 Al (s) + 3 Ni^2+ (aq) --> 2Al^3+ (aq) + 3Ni (s)

(a) What is being oxidized, and what is being reduced? (

b) Write the half-reactions that occur in the two half-cells.

(c) Which electrode is the anode, and which is the cathode? (

d) Indicate the signs of the electrodes

(e) Do electrons flow from the aluminum electrode to the nickel electrode or from the nickel to the aluminum?

(f) In which directions do the cations and anions migrate through the solution? Assume the Al is not coated with its oxide.

Answer 1

a) the oxidation state of aluminum change from 0 to + 3 and oxidation state of nickel change from +2 to 0. From this, we concluded that aluminum gets oxidized because it is losing electrons and nickel get reduced because it is gaining electrons.

b) half-cell reaction of aluminum -

Al_(s) -------------------> Al ⁺³ + 3 e ^-

half-cell reaction of nickel

Ni ⁺² + 2 e^- --------> Ni _(s)

c) reduction occurs at cathode and oxidation occurs at an anode. therefore aluminum electrode anode because aluminum is oxidized and nickel electrode is cathode because nickel is reduced.

d) oxidation of Aluminum occurs which produce electrons and that electrons build up a negative charge. thus the aluminum electrode (anode) is negative. a nickel electrode which gets reduces that means it is consuming electrons and leaving behind positive metals ions and that's lead to a positive charge. thus nickel electrode (cathode) is positive.

e) electron flow from the aluminum electrode to the nickel electrode because aluminum electrode loses electrons and nickel gain electrons which are negatively charged, so electrons move toward the positive end of a cell.

f) In a cell, a salt bridge allows migrating the ions from one half-cell to other half-cells without mix the solution. In a voltaic cell, the cations migrate from anode to cathode while anions migrate from cathode to anode.

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