C4 - electrochemistry

-decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current

-cell - longer side is positive terminal -anode - positive electrode -cathode - negative electrode -electrolyte - molten/ aqueous substance that undergoes electrolysis -external circuit: cell -internal circuit - electrodes, electrolyte -electrical E to chemical E

-graphite/ platinum -inert so that they aren’t involved in the reaction -PANCake Positive Anode, Negative Cathode

CAThode - CATion, metal/ hydrogen, object, pure, water ANode - ANion, non-metals (no hydrogen), metal, impure, hydrogen ions

-current - ( + ) ( - ) -electron - ( - ) ( + ), cathode to anode

-OIL RIG -anode - anions gain electrons - oxidation -cathode - cations lose electrons - reduction eg. oxidation - 2Pb ——> 2Pb+ + 2e- reduction - 2Br+ + 2e- ——> Br2

-electrons - external circuit -ions - electrolyte

-Cathode - if jewelry metal (Cu, Ag, Au, Pt, W), metal is produces; else, Hydrogen gas produced -Anode - if has halide ion, halogen gas is produces; else, oxygen gas produced -if electrolyte is molten, only 2 types of molecules -if electrolyte is aqueous, 4 types of molecules -metals or hydrogen are formed at cathode -non-metals (other than hydrogen) are formed at anode

-2H+ + 2e- —–> H2 (g) -4OH—–> O2 (g) + 2H2O + 4e-

-cathode - object -anode - metal

-cathode - pure -anode - impure

-Copper sulfate as electrolyte -cathode: pure copper at cathode -anode: impure copper -solid copper become ions in solution & goes to cathode -copper ions in solution go to cathode -impurities fall -cannot have a halide in the electrolyte

-electrodes aren’t inert -cathode - less reactive metal - reduction -anode - more reactive metal - oxidation - shrink in size -greater reactivity difference between metals, more Voltage produced -chemical E to electrical E

-uses hydrogen & oxygen to produce electricity & water -membrane is btw platinum electrodes -hydrogen & oxygen is pumped in the membrane -excess hydrogen & water is pumped out -motor is connected to the electrodes & electrons flow through the external circuit

-cathode: 4H+(aq) + 4e- + O2(g) → 2H2O(l) -anode: 2H2(g) → 4H+(aq) + 4e- -overall: 2H2(g) + O2(g) → 2H2O(l)

-no power lost in transmission as there are less moving parts than an internal combustion engine -Produces a voltage as long as it’s supplied with hydrogen & oxygen -only product is water, not a greenhouse gas. -doesn’t need recharging using mains electricity -no moving parts -quieter than a petrol or diesel engine. -fits into an engine bay.

-hydrogen must be stored in the car & is explosive -hydrogen will run out/need replacing. -few hydrogen stations for refueling (unlike electrical outlets) -If the hydrogen is manufactured from coal or natural gas, carbon dioxide is produced -uses expensive platinum electrodes