Problem 3 - Chemistry An Atoms First Approach

Question

You want to "plate out" nickel metal from a nickel nitrate solution onto a piece of metal inserted into the solution. Should you use copper or zinc? Explain.

Step-by-Step Solution

Answer

You should use copper to plate out nickel metal from the nickel nitrate solution. This is because copper has a higher standard reduction potential (+0.34 V) than nickel (-0.25 V), indicating a greater tendency for reduction to occur at the electrode surface. Zinc would not be effective as its reduction potential is lower than that of nickel, and it would more likely dissolve into the solution instead of plating the nickel.

Step 1: Recall the reduction half-reactions and potentials

To solve this problem, we need to recall the reduction half-reactions and their standard reduction potentials (E°) for the involved metals. We have: - Copper (Cu): \( Cu^{2+} + 2e^- \rightarrow Cu(s), \) \(E° = +0.34 V\) - Zinc (Zn): \( Zn^{2+} + 2e^- \rightarrow Zn(s), \) \(E° = -0.76 V\) - Nickel (Ni): \( Ni^{2+} + 2e^- \rightarrow Ni(s), \) \(E° = -0.25 V\)

Step 2: Compare reduction potentials

Now, we compare the standard reduction potentials of copper, zinc, and nickel. A positive potential indicates a greater tendency for reduction to occur at the electrode surface, while a negative potential indicates a lower tendency. Looking at the values, we can see that copper has the highest potential, nickel has the intermediate potential, and zinc has the lowest potential. When two metals are placed in contact with each other in a solution, the metal with the higher potential will have a better chance of reducing the ions in solution.

Step 3: Determine the best metal for plating out nickel

Since the goal is to plate out nickel metal from a nickel nitrate solution, we should choose the metal with a higher reduction potential than nickel. In this case, copper has a higher potential (+0.34 V) than nickel (-0.25 V). Therefore, you should use copper to plate out nickel metal from the nickel nitrate solution. Using zinc would not be effective since its reduction potential is lower than that of nickel, and zinc would more likely dissolve into the solution instead of plating the nickel.