S.6 Electrochemistry Caltec S.6

Lawrence arum , lawry50@gmail.com , watsap /telegram +256 -750513312 Page 1 ELECTROCHEMISTRY Some common terms: Electrolysis . Is the decomposition of molten or aqueous compounds when electricity is passed through them. Electrolyte ; Is a substance which in molten or aqueous state conducts electricity. Electrolytes are divided into ; a) True electrolytes : conduct electricity both in molten and aqueous state (form) e .g. NaCl, KNO 3, etc. b) Potential electrolytes : conduct electricity only in aqueous solution e .g. HCl c) Weak electrolytes : least poorly conduct electricity due to partial ionizati on or dissociation in aqueous solution , providing a small number of aqueous ions. E.g. ethanoic acid, Benzoic acid, ammonia solution, carbonic acid, phenols. d) Strong electrolytes : readily conduct electricity due to almost complete ionization or dissociati on in aqueous solution , providing discret e ions.E .g. NaCl, KNO 3, Ca( OH)2, etc Elect rode : a) Cathode: Electrodes towards which cations move during electrolysis b) Anode: electrodes towards which anions move during electrolysis Electrolytic cell:  Is a chemical setup in which electrolysis occurs.  Electric current causes chemical change/ decomposition of the compound. Typical electrolytic cell FACTORS AFFECTING SELECTIVE DISCHARGE AT THE ELECTRODE Position of the electrochemical series/reactivity ser ies Ions lower down in the electrochemical series/ion with low er electrode potential are discharged in preference to those high up or with high er electrode potential. K+, Na2+, Ca2+, Mg2+, Al3+, Zn2+, Fe2+, Sn2+, Pb2+, H 3O+, Cu2+, Ag+, Au+ Ease of discharge increases 𝑂 H, I−, Br−, Cl−, NO− 3, SO2− 4, F− 𝐸𝑎𝑠𝑒 𝑜𝑓 𝑑𝑖𝑠𝑐𝑔𝑎𝑟𝑔𝑒 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒𝑠 Concentration Increase in concentration of an ion increases its chances of being discharged . E.g. in the elect rolysis of brine (concentrated solution of NaCl) using inert electrodes; -Ions present are Na+ and Cl−, H+ and …