A steel key is electroplated with nickel to stop it corroding. The key is one electrode, a bar of nickel is the other electrode, and the electrolyte is nickel sulfate solution, which contains Ni2+\mathrm{Ni^{2+}}Ni2+ ions.
Which row is correct for this process?
At the key: Ni2++2e−→Ni\mathrm{Ni^{2+} + 2e^{-} \rightarrow Ni}Ni2++2e−→Ni; the nickel bar loses mass; the Ni2+\mathrm{Ni^{2+}}Ni2+ concentration stays the same
At the key: Ni→Ni2++2e−\mathrm{Ni \rightarrow Ni^{2+} + 2e^{-}}Ni→Ni2++2e−; the nickel bar gains mass; the Ni2+\mathrm{Ni^{2+}}Ni2+ concentration stays the same
At the key: Ni2++2e−→Ni\mathrm{Ni^{2+} + 2e^{-} \rightarrow Ni}Ni2++2e−→Ni; the nickel bar loses mass; the Ni2+\mathrm{Ni^{2+}}Ni2+ concentration decreases
At the key: Ni2++2e−→Ni\mathrm{Ni^{2+} + 2e^{-} \rightarrow Ni}Ni2++2e−→Ni; the nickel bar is unchanged; the Ni2+\mathrm{Ni^{2+}}Ni2+ concentration decreases
42 exam-style questions on Edexcel GCSE Chemistry 6.1 Transition metals, alloys and corrosion, covering 6.1.1 Properties of transition metals, 6.1.2 Corrosion and its prevention, and 6.1.3 Alloys and the uses of metals. Each one has a worked solution and a mark scheme showing where the marks go.