Question involving standard reduction potentials and sacrificial electrodes. Can

Question

Question involving standard reduction potentials and sacrificial electrodes. Can someone please help?

1. Place the following solutions in order of increasing expected reactivity with a zinc-plated galvanized nail. Use standard reduction potentials. Which would react slowest with zinc as #1 leading up to which woudl react fastest as #4. Cr(NO3)3 NaNO3 Cu(NO3)2 Pb(NO3)2

2. Make 3 matches with the following metals and a substance that may act as a sacrifical electrode. All 3 metals have unique choices and you CANNOT reuse choices. (If you pair sodium metal with A, you cannot use A again for another metal).

Sodium metal ____

Iron metal _______

Silver metal ______

A. Tin - sacrifical electrode

B. Aluminum - sacrifical electrode

C. Barium - sacrifical electrode

D. Postassium metal

E. Gold - sacrifical electrode

Explanation / Answer

1)

In order to solve this we must know standard reduction potentials of each system,

Cr3+/Cr = - 0.74 V

Na+/Na = - 2.71 V

Cu2+/Cu = 0.34 V

Pb2+/Pb = - 0.13 V

and the standard reduction potential of Zn2+/Zn = - 0.76 V

So Zn can be displaced by the solutions which have more reduction potential than Zn2+/Zn.

The order of reactivity towards Zn is

#1 Na+/Na < Cr3+/Cr < Pb2+/Pb < Cu2+/Cu #4

2)

Sodium metal -  Barium - sacrifical electrode

Iron metal - Aluminum - sacrifical electrode

Silver metal -  Tin - sacrifical electrode

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