1.11 electrode potentials

• What are the advantages of fuel cells?

  No recharging needed.

  
  

  H2O is the only product.
• What is the conventional cell diagram for a hydrogen oxygen fuel cell.

  Pt | H2 | H2O || O2 | OH- | Pt
• What side of the electrochemical cell is negative?

  Left
• What side of the electrochemical cell is oxidation?

  Left
• Which way do electrons flow in an electrochemical cell?

  Left to right until concs are equal
• What are the standard conditions for electrochemical cells?

  All solutions have the concentration of 1 mol dm^3

  
  

  298K

  
  

  100KPa

  
  

  Platinum electrode if there is no metal
• What is the salt bridge made of in electrochemical cells?

  Filter paper soaked in KNO3
• How is the value of E changed when concentration of X increases?

  Use le chateliers principle

  
  

  A change which favour reduction will make E more positive

  
  

  A change which favours oxidation will make E more negative
• Why are the calculated EMFs not always achieved?

  Non standards conditions

  
  

  Current flow affects voltage
• What are the three types of cells?

  Rechargeable, non rechargeable, fuel
• What is needed of the soluble ionic compound used in the salt bridge?

  Must be unreactive with the electrolyte and solution in the beaker.
• Define standard electrode potential.

  The potential of a redox system to lose or gain electrons compared to the standard hydrogen electrode.
• What is the purpose of the salt bridge?

  allow ions to flow back and forth so that charge does not build up
• What are the advantages of rechargeable batteries?

  Cheaper in the long term

  
  

  Recyclable
• Disadvantages of fuel cells

  Expensive as H2 is produced by electrolysis of water

  
  

  Dangerous as H2 is highly flammable
• In a half cell with no metal what is the electrode made from?

  Platinum
• Advantages of non chargeable batteries?

  Cheaper

  
  

  Work for longer

  
  

  Can be recycled

  
  

  Less dangerous as don't contain lead.
• Why is platinum used as an electrode?

  It is inert and conducts electricity
• What format are reactions written as in the electrochemical series?

  Reduction
• When a metal is present what electrode is used?

  The metal, and the solution is its ions.
• What does the electrode potential tell us?

  How easily the half cell gives up its electrons / how easily it is oxidised.
• In electrochemical equations, what happens to the most negative one?

  Oxidised
• In electrochemical equations what happens to the most positive one?

  Reduced
• When turning two half equations into one which way do you write them?

  Most positive gets written forward and negative gets written backwards
• What is EMF?

  Electromotive force: the electrical pressure that causes electrons to flow through the conductor.
• When writing cell notations what does the | mean?

  Change in state, if no change is state occurs use a comma
• In cell notations what does || mean?

  Salt bridge
• In cell notations which half cell goes on the left?

  Most negative
• How do you calculate EMF?

  Potential on the right - potential on the left.
• Are very positive half cells better oxidising or reducing agents?

  Oxidising, they will oxidise anything below it (more negative) in the series
• Are very negative half cells better oxidising or reducing agents?

  Reducing, they will reduce anything more positive than it
• What is the effect of increasing pressure on a cell?

  EMF more negative