Cathodic protection of iron involves using another more reactive metal as a sacrificial anode. Classify each of the following metals by whether they would or would not act as a sacrificial anode to iron.

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Ag
Mg
Cu
Pb
Sn
Zn
Au

a. Will act as sacrificial anode for iron
b. Will not act as sacrificial anode for iron

Explanation:

Materials used for sacrificial anodes must be relatively pure active metals.

Or we can say any metal with more negative potential that that of iron ( +0.59) is used for sacrificial anode for iron

so from the above the following can be used as sacrificial anode for iron

Mg = +1.06

Al = +0.96

Zn = +0.7

The following will not be used as sacrificial anode for iron because their negative reduction potential is less than that of iron ( +0.59)

Ag = -0.76

Cu = -0.44

Pb = 0

Sn = +0.34

Au = -3.05

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"