Chem Topic 5

• Which reaction profile is this?

  Exothermic

  
• Which reaction profile is this?

  Endothermic

  
• What is an endothermic and exothermic reaction?

  Exothermic - releases heat in the form of energy to surroundings, which causes it to get hotter

  Endothermic - takes in energy from surroundings, which causes it to become colder
• What is bond energy and how can it be calculated?

  Every bond requires a specific amount of energy to break it. We can calculate it via:

  Bond energy = bonds broken - bonds formed

  Negative end value = exothermic reaction

  Positive end value = endothermic reaction
• What do cells contain?

  Chemicals that, when they react, produce a potential difference that can power electrical devices
• What is a battery?

  Multiple cells connected to each to each other
• What are non-renewable cells/batteries?

  Cells/batteries that cannot be used again once all chemicals have been used up
• What are renewable batteries?

  Batteries that are able to perform the reverse reaction when a p.d. is supplied
• What is a hydrogen fuel cell?

  A hydrogen fuel cell is a device that converts hydrogen and oxygen into water, producing electricity in the process.
• What are the pros and cons of the different cell types?

  Alkaline:

  Pros: Cheaper to manufacture

  Cons: May end up in landfill once fully discharged, expensive to recycle

  Rechargeable cell:

  Pros: Can be recharged many times before recycled, reducing use of resources

  Cons: Costs more to manufacture

  Hydrogen fuel cell:

  Pros: Easy to maintain due to no moving parts, small size and water is only chemical product

  Cons: Very expensive to manufacture; needs a constant supply of hydrogen fuel which is a flammable gas
• What is the half equation for the cathode in a hydrogen fuel cell?

  
• What is the half equation for the anode in a hydrogen fuel cell?