An electrolytic cell is set up to plate nickel metal onto a steel key

CHEMISTRY · Multi-part · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry

Problem

An electrolytic cell is set up to plate nickel metal onto a steel key. The cathode is the key, and the anode is a nickel strip. Both electrodes are immersed in 1.0 M

\text{NiCl}_{2}

solution contained in one compartment that is separated from a second compartment filled with 1.0 M

\text{KNO}_{3}

solution by a salt bridge. A direct-current power supply forces the non-spontaneous reaction to occur. At the operating current,

\text{Ni}^{2+}

ions are reduced at the cathode according to

\text{Ni}^{2+}(aq)+2e^{-}\rightarrow \text{Ni}(s)

. (a) Describe the direction of electron flow in the external wires relative to the key and the nickel strip when the power supply is on. (b) Identify which ion in the salt bridge (

\text{K}^{+}

\text{NO}_{3}^{-}

) migrates toward the cathode compartment and which migrates toward the anode compartment. Justify each choice with reference to the reactions occurring at the electrodes. (c) Predict the qualitative change in concentration of

\text{Ni}^{2+}

ions in the cathode compartment as electrolysis proceeds. Explain how the ion migration you stated in part (b) supports this change.

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