Question

(a) Based on standard reduction potentials, would you expect copper metal to oxidize under standard conditions in the presence of oxygen and hydrogen ions? (b) When the Statue of Liberty was refurbished, Teflon spacers were placed between the iron skeleton and the copper metal on the surface of the statue. What role do these spacers play?

Short answer

(a) Yes, copper metal would oxidize under standard conditions in the presence of oxygen and hydrogen ions, as the overall reaction is spontaneous with a positive ΔE° value of 1.57V. (b) The Teflon spacers placed between the iron skeleton and the copper surface of the Statue of Liberty prevent galvanic corrosion by eliminating physical and electrical contact between the two metals. This intervention ensures the structural stability and longevity of both the iron skeleton and the copper surface of the statue.

Step-by-step solution

Determine the relevant half-reactions

Before analyzing whether copper will oxidize in the presence of oxygen and hydrogen ions, we need to identify two half-reactions. The copper half-reactions are: 1. Copper oxidation: \(Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-\) 2. Oxygen reduction in the presence of hydrogen ions (forming water): \(O_2(g) + 4H^{+}(aq) + 4e^- \rightarrow 2H_2O(l)\)

Check the standard reduction potentials

To determine if a reaction is spontaneous under standard conditions, we need to check the standard reduction potentials for both half-reactions. The values are given as: 1. Copper oxidation: \(E°(Cu^{2+}/Cu) = +0.34 V\) (this value represents the reduction half-reaction, our reaction is the reversed one) 2. Oxygen reduction: \(E°(O_2/H_2O) = +1.23 V\)

Check if the overall reaction is spontaneous

We can determine if the overall reaction is spontaneous by comparing the standard reduction potentials of both half-reactions. In this case, \(E°(O_2/H_2O) > E°(Cu^{2+}/Cu)\), implying that the oxygen reduction reaction is more likely to happen compared to copper oxidation. To get the net voltage, we then need to subtract the higher reduction potential from the lower value: \(ΔE° = E°(O_2/H_2O) - (-E°(Cu^{2+}/Cu)) = 1.23 - (-0.34) = 1.57V\) Since ΔE° is positive, it indicates that the overall reaction is spontaneous under standard conditions, and copper will oxidize in the presence of oxygen and hydrogen ions. (a) The answer is YES. Copper metal would oxidize under standard conditions in the presence of oxygen and hydrogen ions.

Explain the role of Teflon spacers

(b) The Teflon spacers play an essential role in preventing galvanic corrosion between the iron skeleton and the outer copper surface of the Statue of Liberty. Galvanic corrosion occurs when two dissimilar metals, such as iron and copper, are in physical or electrical contact with each other and an electrolyte (such as saltwater or rain). The electrolyte facilitates electron transfer between the two different metals, resulting in corrosion of the least corrosion-resistant metal, which in this case would be iron. By placing Teflon spacers between the iron skeleton and the copper surface, physical and electrical contact between the two metals is prevented. This intervention eliminates the galvanic corrosion process, ensuring the structural stability and longevity of both the iron skeleton and the copper surface of the statue.