WJEC Chemistry for A2: Student Bk

Content 11 Redox Reactions 12 Cells and half-cells 14 Standard electrode potentials 16 Feasibility of reactions 18 Fuel cells You should be able to demonstrate and apply your knowledge and understanding of: The definitions of redox reactions in terms of electron transfer. Using ion/electron half-equations to represent redox systems. Building half-cells into cells and showing these as cell diagrams. The concept of standard electrode potentials and the role of the standard hydrogen electrode in finding these. Half-cells based on metal/metal ion electrodes and electrodes based on different oxidation states of the same element. How simple electrochemical cells are formed by combining electrodes. The concept of cell EMF and how it can be used to deduce the feasibility of reactions. The principles of the hydrogen fuel cell and its benefits and drawbacks. Chemists organise the properties and reactions of materials to see patterns and make predictions. One way to classify reactions is as oxidation with the name linked to the original definitions as processes that gained oxygen. The opposite reaction, reduction, referred to the loss of mass when oxygen was removed from a compound. Over time chemists have adjusted their ideas of oxidation and reduction as their understanding of the processes have developed, so the focus is now on electrons in the definitions of these terms. The harnessing of flows of electrons between compounds is key to the function of the batteries used to power all the mobile devices used today. 3.1 Redox and standard electrode potential Unit 3 10