Chemical Changes

• Number of moles= mass / molar mass
• A pipette can be used to measure liquid more accurately
• Reactivity series:

  
• Oxygen can be removed from zinc oxide via reduction with carbon
• A reduction is when oxygen is removed from a substance
• Carbon is in between aluminium and zinc in the reactivity series
• % atom economy = (mass of desired product/ mass of all reactants ) x 100
• ore=rock that contains enough metal to make it economical to extract
• sulphur dioxide (SO2) can cause acid rain
• Recycling copper leads to less acid rain pollution and keeps copper reserves lasting for longer
• Disadvantages of recycling copper: collection problems, transport problems
• Metals that do not need to be extracted from ore are called native metals
• Iron oxide is reduced to make iron by heating with high temperatures before carbon react with oxygen and CO reacts with the ore
• Redox reaction is a reaction where both reduction and oxidation happen
• Diagram of how the student sets up her experiment to pass electricity through the solutions of dilute ionic compounds.

  
• Electrolysis is the process by which ionic substances are decomposed into simpler substances when an electric current is passed through them
• In the electrolysis of Copper Chloride, chlorine is the product at the positive electrode because chloride ions are negative. Copper is the product of the negative electrode as the copper ions are positive
• Equipment for electrolysis: Beaker, Electrolyte, Electrodes, Wire to join electrodes, power supply (battery)
• An electrolyte is a liquid or solution that contains an ionic compound and the ions are free to move in
• If the compound in electrolysis is soluble then you can dissolve it in water
• The the compound in electrolysis is insoluble then you have to melt it into a molten liquid. This is a way to make sure that the ions can move around
• Electrodes are solid conductors usually made out of metal or carbon
• The positive electrode is called the anode
• The negative electrode is called the cathode
• The electrodes are joined by a wire which allows electrons to pass between them
• The battery in electrolysis drives the flow of electrons
• In electrolysis the current passed through the electrolyte splits the reactant
• Because the negative ions are attracted to the positive electrode they go to it where they are discharged which means they go from a charged ion to a neutral atom. The same thing will happen for the negative electrode but in reverse
• An oxidation reaction is where there is a loss of electrons
• Graphite is used for electrons because...

  • It is inert
  • It conducts electricity
• Copper can be reused and recycled so shouldn't be dumped
• Easiest way to reduce is by reduction with carbon
• Reduction with carbon works as the carbon displaces the the metal in the metal oxide to form pure metal and carbon dioxide
• Reduction with carbon only works if carbon is more reactive than the current metal
• If carbon isn't reactive enough to displace the other metal then electrolysis has to be used. This is much more expensive
• Electrolysis only works if the ions are able to move
• Aluminium oxide has to be melted before it can undergo electrolysis as it is a solid and also is contained inside a ore( bauxite )
• How to make Aluminium oxide molten:

  
• Equipment for electrolysis:

  • Beaker
  • Electrolyte
  • 2 electrodes (1 anode and 1 cathode)
  • Wire
  • Some sort of power source ( maybe a battery )
• The electrodes are made out of carbon and allow electrons to pass through