Electrolysis

• Electrolysis involves using electricity to break down electrolytes to form elements.
• The products of electrolysis can be predicted for a given electrolyte.
• Electrolytes are substances which, when molten or in solution, will conduct an electric current.
• An ionic compound occurs when a negative ion (an atom that has gained an electron) joins with a positive ion (an atom that has lost an electron).
• Molten is a term used to describe a liquid substance (eg rock, glass or metal) formed by heating a solid state (heated so they become liquids), or dissolved.
• A substance is said to be dissolved when it breaks up and mixes completely with a solvent to produce a solution.
• An ion in electrolytes is an electrically charged particle, formed when an atom or molecule gains or loses electrons.
• In electrolytes, ions are free to move within the liquid or solution.
• Electrolysis is the decomposition (breakdown) of a compound using an electric current.
• Electrolysis is a process in which electrical energy, from a direct current supply, breaks down electrolytes.
• The free moving ions in electrolytes are attracted to the oppositely charged electrodes.
• The negatively charged electrode in electrolysis is called the cathode.
• Positively charged ions move towards the cathode during electrolysis.
• Negatively charged ions move towards the anode during electrolysis.
• Products of electrolysis are formed when ions reach an electrode, they gain or lose electrons.
• An atom is the smallest part of an element that can exist.
• A molecule is a collection of two or more atoms held together by chemical bonds.
• An element is a substance made of one type of atom only.
• Positive ions gain electrons from the negatively charged cathode during electrolysis.
• Negative ions lose electrons at the positively charged anode during electrolysis.
• Molten lead bromide, PbBr 2 (l), is an electrolyte used in electrolysis.
• During electrolysis, Pb 2+ ions gain electrons at the cathode and become Pb atoms, while Br - ions lose electrons at the anode and become Br atoms, which pair up to form Br 2 molecules.
• Lead forms at the negative electrode and bromine forms at the positive electrode during the electrolysis of molten lead bromide.
• Positively charged calcium ions move to the negative electrode during electrolysis, gain electrons to form calcium atoms, and so calcium is formed at the negative electrode.
• Negatively charged chloride ions move to the positive electrode during electrolysis, lose electrons to form chlorine atoms, and the atoms join up in pairs to form Cl 2 molecules, so chlorine gas is formed at the positive electrode.
• During the electrolysis of molten salts, a metal forms at the cathode and a non-metal forms at the anode.
• Aluminium will form at the negative electrode and oxygen will form at the positive electrode during the electrolysis of molten aluminium oxide.