Electrode potentials and cells

• Electrochemical cells

  • consists of 2 solutions with metal electrodes and a salt bridge
• Salt bridge

  • filter paper soaked in potassium nitrate
  • Completes the circuit, allowing a flow of ions
• What are the specific rules for conventional cell representation?

  • Most negative potential on the left
  • Most oxidised species next to salt bridge
  • Salt bridge shown with a double line
  • Include state symbols
• Conventional cell representation

  
• Standard Hydrogen Electrode (SHE)

  • platinum electrode
  • hydrogen gas
  • [HCl] of 1 moldm-3
  • 100kpa and 298k
• SHE diagram example

  
• $Emf_{\left(cell\right)}\ =$$\ E°_{\left(right\right)}\ -\ E°_{\left(left\right)}$
• Rechargeable cells

  • reversible reactions
  • Used in phones, laptops and cars
  • Lithium ion cells: consists of a lithium cobalt oxide electrode, a graphite (carbon) electrode and a lithium salt electrolyte

  
• Fuel cell

  • generates a current without needing to be recharged
  • Hydrogen fuel cell: uses a continuous supply of hydrogen and oxygen from the air to generate a continuous current
  • Environmentally friendly as water is the only waste product
  • However, expensive and highly flammable