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.

Short answer

Zinc should be used instead of copper for the plating process because it has a more negative reduction potential (\(E°_{Zn} = -0.76 V\)), making it more reactive than copper (\(E°_{Cu} = +0.34 V\)). This higher reactivity will allow zinc to more easily lose electrons, enabling the deposition of nickel metal from the nickel nitrate solution.

Step-by-step solution

Identify the Metals' Standard Reduction Potentials

The first step is to identify the standard reduction potentials of the metals in question, which will allow us to determine which metal is more reactive. The standard reduction potentials of copper, zinc, and nickel are as follows: Copper (Cu): \[E°_{Cu} = +0.34 V\] Zinc (Zn): \[E°_{Zn} = -0.76 V\] Nickel (Ni): \[E°_{Ni} = -0.25 V\]

Compare the Reactivities

Next, compare the reactivity of the metals by comparing their standard reduction potentials. Remember that the more negative the reduction potential, the more likely a metal is to lose electrons, which is indicative of its reactivity. Since \(E°_{Zn} = -0.76 V\) and \(E°_{Cu} = +0.34 V\), it is clear that zinc (\(Zn\)) has a more negative reduction potential than copper (\(Cu\)). Consequently, zinc is more reactive than copper.

Choose the Metal for the Plating Process

Given that zinc is more reactive than copper, when placed in a nickel nitrate solution, zinc would be more likely to lose electrons. This would result in the zinc dissolving into the solution and the nickel ions in the solution gaining electrons and depositing as metallic nickel onto the zinc metal surface. Therefore, to plate out nickel metal from a nickel nitrate solution, zinc should be used instead of copper.