A student investigates the electrolysis of an aqueous solution containing a mixture of 1.0 mol dm-3 concentrations of zinc nitrate, copper(II) nitrate, and silver nitrate using inert carbon electrodes as shown in the diagram.
The standard electrode potentials for the metal species are:
Ag+(aq)+e−⇌Ag(s)Eθ=+0.80 V \text{Ag}^+(aq) + e^- \rightleftharpoons \text{Ag}(s) \quad E^\theta = +0.80\text{ V} Ag+(aq)+e−⇌Ag(s)Eθ=+0.80 V Cu2+(aq)+2e−⇌Cu(s)Eθ=+0.34 V \text{Cu}^{2+}(aq) + 2e^- \rightleftharpoons \text{Cu}(s) \quad E^\theta = +0.34\text{ V} Cu2+(aq)+2e−⇌Cu(s)Eθ=+0.34 V Zn2+(aq)+2e−⇌Zn(s)Eθ=−0.76 V \text{Zn}^{2+}(aq) + 2e^- \rightleftharpoons \text{Zn}(s) \quad E^\theta = -0.76\text{ V} Zn2+(aq)+2e−⇌Zn(s)Eθ=−0.76 VWhich product is deposited first at the cathode, and which reaction occurs at the anode?
Cathode product: Zn(s)\text{Zn}(s)Zn(s); Anode reaction: Zn(s)→Zn2+(aq)+2e−\text{Zn}(s) \rightarrow \text{Zn}^{2+}(aq) + 2e^-Zn(s)→Zn2+(aq)+2e−
Cathode product: Ag(s)\text{Ag}(s)Ag(s); Anode reaction: 2H2O(l)→O2(g)+4H+(aq)+4e−2\text{H}_2\text{O}(l) \rightarrow \text{O}_2(g) + 4\text{H}^+(aq) + 4e^-2H2O(l)→O2(g)+4H+(aq)+4e−
Cathode product: Cu(s)\text{Cu}(s)Cu(s); Anode reaction: Cu2+(aq)+2e−→Cu(s)\text{Cu}^{2+}(aq) + 2e^- \rightarrow \text{Cu}(s)Cu2+(aq)+2e−→Cu(s)
Cathode product: Ag(s)\text{Ag}(s)Ag(s); Anode reaction: 2NO3−(aq)→N2(g)+3O2(g)+2e−2\text{NO}_3^-(aq) \rightarrow \text{N}_2(g) + 3\text{O}_2(g) + 2e^-2NO3−(aq)→N2(g)+3O2(g)+2e−
Electrolytic processes Questions
Practise Edexcel GCSE Chemistry Electrolytic processes with exam-style questions for Foundation and Higher tier. 100 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.