Chemical Cells

• What do chemical cells use to transfer energy?

  Chemical reactions
• What factors affect the voltage of a chemical cell?

  Electrode materials and electrolyte substance
• How can a simple cell be created?

  By connecting two different metals with an electrolyte
• What is a battery made of?

  A number of cells connected in series
• What happens to non-rechargeable cells when reactants are used up?

  The battery 'goes flat'
• How do rechargeable cells work?

  The chemical reactions can be reversed
• What happens when you swap the electrodes in a cell?

  The recorded voltage becomes negative
• When does a cell have the highest voltage?

  When the reactivity difference of metals is largest
• What is the expected voltage of a cell made using magnesium and silver?

  Higher than magnesium and copper
• How do fuel cells differ from chemical cells?

  Fuel cells produce voltage continuously.
• What is required for fuel cells to produce voltage?

  A constant supply of fuel and oxygen.
• How is fuel oxidized in fuel cells?

  Electrochemically, not by burning.
• What type of energy is released by fuel cells?

  Electrical energy, not thermal energy.
• What is the main product of hydrogen-oxygen fuel cells?

  Water
• What is the overall reaction in a hydrogen-oxygen fuel cell?

  Hydrogen + Oxygen → Water
• What is the balanced equation for the reaction in a hydrogen-oxygen fuel cell?

  $2H_2(g) +$$O_2(g) \rightarrow 2H_2O(l)$
• What happens at the negative electrode of a hydrogen-oxygen fuel cell?

  2H2 + 4OH- → 4H2O + 4e-
• What happens at the positive electrode of a hydrogen-oxygen fuel cell?

  O2 + 2H2O + 4e- → 4OH-
• What is the overall equation after combining the half equations in a hydrogen-oxygen fuel cell?

  2H2 + O2 → 2H2O
• Why do hydroxide ions and electrons cancel in the overall equation?

  They appear on both sides of the equation.
• What is the state of water produced in the hydrogen-oxygen fuel cell reaction?

  Liquid (l)
• What is a pro of alkaline cells?

  Cheaper to manufacture
• What is a con of alkaline cells?

  May end up in landfill sites
• What is a pro of rechargeable cells?

  Can be recharged many times
• What is a con of rechargeable cells?

  Costs more to manufacture
• What is a pro of hydrogen fuel cells?

  Easy to maintain with no moving parts
• What is a con of hydrogen fuel cells?

  Very expensive to manufacture
• What are the strengths and weaknesses of fuel cells?

  Strengths:

  • Vary based on intended use
  • Used in spacecraft and vehicles

  
  

  Weaknesses:

  • Depend on fuel supply
  • Costly to manufacture
• What type of fuel cells are used in spacecraft?

  Hydrogen-oxygen fuel cells
• What is a benefit of the water produced by hydrogen-oxygen fuel cells in spacecraft?

  It is useful as drinking water for astronauts
• What is a potential problem for hydrogen-oxygen fuel cells in spacecraft?

  Need a constant supply of hydrogen fuel
• How do spacecraft in orbit replace hydrogen and oxygen for fuel cells?

  Through electrolysis of water using solar cells
• When do solar cells work in spacecraft?

  Only when they are in the light
• What advantage do fuel cells provide when spacecraft are in the dark?

  Allow electricity production even in darkness