electrolysis topic

• in an ionic solid the ions are fixed meaning that no electricity can flow.
• if molten or in a solution the ions are free to move so electricity can flow
• an electrolyte is a solution containing ions which allow current to flow
• when an ionic substance is melted or dissolved in water the ions are then free to move
• the positive electrode is called the anode
• the negative electrode is called the cathode
• positive ions move to the cathode
• negative ions move to the anode
• electrolysis is needed for the extraction of metals more reactive than carbon
• the main disadvantage of using electrolysis is that it requires a lot of energy to melt the compounds and to produce the electricity needed
• during the electrolysis of solutions either halogens or oxygen is produced at the anode
• in the electrolysis of sodium chloride solution chlorine gas and hydrogen gas are the products
• the anode needs to be replaced within the electrolysis of aluminium oxide because the oxygen reacts with the carbon electrode to produce carbon dioxide so therefore burns away
• in the electrolysis of aluminium oxide, aluminium is produced at the cathode and oxygen is produced at the anode
• cryolite is mixed with aluminium oxide when extracting aluminium to lower the melting point
• negative ions losing electrons to become atoms is called oxidation
• positive ions gaining electrons to become atoms is called reduction
• some uses of aluminium is for foil, building materials, bikes and cans
• aluminium is found in the ionic compound aluminium oxide which is found in the ore bauxite
• electrolysis is more complex in aqueous solutions as the water ionises and seperates into H+ ions and OH- ions. This means that there is more than one ion attracted to each electrode
• if the - ion is not a halogen then the hydroxide ions from the water are discharged to make water and oxygen gas. The other ions stay in the solution
• the positive electrode is used up in the experiment because the oxygen reacts with the carbon electrode and produces carbon dioxide which burns away the positive electrode.