NJC 2026 Electrochemistry Part 1 (Student)

National Junior College SH2 H2 Chemistry 1 Electrochemistry Electrochemistry is the study of the inter-conversion of chemical and electrical energies. This inter-conversion of energies occurs in cells in which redox reactions (i.e. reactions involving the transfer of electrons from one chemical species to another) produce or utilise electrical energy. Comparison of Electrochemical (Part 1) and Electrolytic cell (Part 2) ELECTROCHEMICAL CELL ELECTROLYTIC CELL Energy change chemical energy → electrical energy electrical energy → chemical energy Cell Reaction Spontaneous Chemical reaction takes place to generate electric current within celll (battery). Non-spontaneous External electric current is applied to drive the reaction to occur. Cathode (reduction) Positive (+) electrode Negative (–) electrode Anode (oxidation) Negative (–) electrode Positive (+) electrode Note: 1. In both electrochemical and electrolytic cells, oxidation always takes place at the anode while reduction always takes place at the cathode. 2. Polarity of electrode always follow the polarity of the battery. [ElectroCHEMICAL cell] The two half-cells form the battery. Anode is the negative terminal of the battery that releases electrons while cathode is the positive terminal of the battery that accepts electrons. [ElectroLYTIC cell] The polarities of the electrode are reversed, as the electrodes follows the polarity of the battery terminal it is connected to. • anode (+ve) is connected to the +ve terminal of battery and attracts anions (−ve) • cathode (−ve) is connected to the −ve terminal of battery and attracts cations (+ve)

National Junior College SH2 H2 Chemistry 2 Electrochemical Cell (Part 1) Content • Redox processes: electron transfer and changes in oxidation number (oxidation state) • Electrode potentials (i) standard electrode (redox) potentials, Eo; the redox series (ii) standard cell potentials, Eo , and their uses (iii) batteries and fuel cells Learning Outcomes Candidates should be able to: (a) describe and explain redox processes in terms of electron transfer and/or of changes in oxidation number (oxidation state) (b) define the terms: (i) standard electrode (redox) potential (ii) standard cell potential (c) describe the standard hydrogen electrode (d) describe methods used to measure the standard electrode potentials of: (i) metals or non-metals in contact with their ions in aqueous solution (ii) ions of the same element in different oxidation states (e) calculate a standard cell potential by combining two standard electrode potentials (f) use standard cell potentials to: (i) explain/deduce the direction of electron flow from a simple cell (ii) predict the spontaneity of a reaction (g) understand the limitations in the use of standard cell potentials to predict the spontaneity of a reaction (h