5.1-electrolysis with inert electrodes

• Electrolytes

  Ionic compounds in the molten state or dissolved in water
• Electrolysis

  Electrical energy from a direct current supply decomposes electrolytes
• Movement of ions during electrolysis

  1. Positively charged cations migrate to the negatively charged cathode

  2. Negatively charged anions migrate to the positively charged anode
• what products are formed when using inert electrodes in the electrolyte copper chloride solution?

  copper and chlorine gas.
• what products are formed when using inert electrodes in the electrolyte sodium sulfate solution?

  hydrogen gas, oxygen gas, and sodium hydroxide.
• what are the two solutions we have to use during electrolysis?

  • copper sulfate solution with inert (graphite) electrodes
  • copper sulfate solution with copper electrodes
• what apparatus do you need?

  -power supply

  -cathode(-)

  -anode(+)

  -inert electrodes

  -beaker
• what is step 1?

  pour copper sulfate solution into a beaker
• what is step 2?

  place 2 graphite rods in copper sulfate solution , attach one electode to the negative terminal of a dc supply and the other electrode to the positive terminal
• what is step 3?

  ensure copper sulfate solution is covering electrodes
• what is step 4?

  turn on the power supply and observe
• what happens at the anode?

  the Cl- is attracted to the anode and causes oxygen to be produced, due to the loss of electrons
• what happens at the cathode?

  reduction, the cu+ gains two electrons and causes cu2 to be fromed making a layer of cu on the electrode, changing the colour from black to orange
• Write the half equation for the formation of the product at the anode and explain whether it is oxidation or reduction.

  $4OH − →O 2 ​ +$$2H 2 ​ O+$$4e −$

  the reaction is oxidation because electrons are being lost
• Write the half equation for the formation of the product at the cathode and explain whether it is oxidation or reduction.

  $Cu 2+$$+$$2e − →Cu$

  • this reaction is reduction because copper ions are gaining 2 electrons
• what happens to the colour of the solution during the electrolysis?

  the colour of the solution changes from blue to colourless as copper ions are reduced and deposited onto the cathode
• if the electrolysis is continued for a long time, what will be left in the solution?

  metal ions.