Topic 5 Higer Flashcards
(19 cards)
What happens when bonds from?
Energy is released
What is required to break bonds?
Energy must be supplied
What is required to create a cell?
- two different metal electrodes
- an electrolyte
What is a battery p?
- two or more cells joined together in series
How does a rechargeable battery function?
- energy is produced via a reversible reaction
- the reaction can be revered when an electrical current is supplies
What is the overall reaction of a hydrogen fuel cell?
H2 + O2 = H2O
What is the half equation at the negative electrode of a hydrogen fuel cell?
O2 + 2H2O + 4e- = 4OH-
What is the half equation at the positive electrode of a hydrogen fuel cell?
2H2 + 4OH- = 4H2O + 4e-
What are the benefits of a hydrogen fuel cell?
- water is the only waste product
- high efficiency
What are the cons of hydrogen fuel cells?
- very expensive to manufacture
- need a constant supply of hydrogen
- hydrogen is very reactive so difficult to transport
What are the pros of a rechargeable cell?
- can be reacharged many times before being recycled
What is the pro of an alkaline battery (non rechargeable)
Cheaper to manufacture
How do you calculate the energy change of a reaction?
Total energy of the reactants - total energy of the products
What should the total energy change of the reaction be if the reaction is exothermic?
Negative
What is the activation energy
The amount of energy required to start reaction
What are some items that use an exothermic reaction
Hand warmer, self heating can
What is a use of an endothermic reaction
Sports injury pack
Which line represents the activation energy
The line from the reactant to the top of the hump
Which line represents the energy change
The line from the reactants to the products
