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chemistry > energy changes > Flashcards

energy changes Flashcards

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1
Q

what is an exothermic reaction

A

when energy is transferred to the surroundings in a chemical reaction

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2
Q

give examples of exothermic reactions

A
  • combustion
  • oxidation
  • neutralisation
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3
Q

what is an endothermic reaction

A

chemical reactions that take heat energy from the surroundings

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4
Q

give an example of an endothermic reaction

A
  • thermal decomposition
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5
Q

what is activation energy

A

the minimum amount of energy the reactant particles need in order to collide with each other and react

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6
Q

what is bond energy

A

the amount of energy required to break one mole of a particular covalent bond

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7
Q

is bond breaking endothermic or exothermic

A

endothermic

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8
Q

is bond forming exothermic or endothermic

A

exothermic

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9
Q

how do you calculate the total energy of the overall reaction

A

energy required to break bonds - energy released by forming bonds

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10
Q

what is a fuel cell

A

a type of electrochemical cell

- converts energy between chemical and electrical

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11
Q

what is the most common type of fuel cell

A

hydrogen-oxygen fuel cell

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12
Q

what is the set up of a fuel cell

A
  • an electrolyte in the centre
  • electrodes on either side which are connected by a wire
  • anode and cathode compartment on opposite sides
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13
Q

what is the positive electrode in a fuel cell

A

cathode

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14
Q

what is the negative electrode in a fuel cell

A

anode

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15
Q

what are electrodes made out of in a fuel cell

A

porous carbon that contain a catalyst

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16
Q

what happens to the hydrogen in a fuel cell

A

it is oxidised at the anode to form H+ ions

17
Q

what happens at the cathode in a fuel cell

A

the positive hydrogen ions react with the oxygen to produce water

18
Q

how do fuel cells generate electricity

A

hydrogen loses electrons which sets up a potential difference across the cell

19
Q

what are the advantages of hydrogen-oxygen fuel cells

A
  • only require hydrogen and oxygen
  • don’t produce any carbon dioxide
  • last longer than batteries
  • less polluting to dispose of
20
Q

what are the disadvantages of hydrogen-oxygen fuel cells

A
  • hydrogen is a gas which makes it harder to store
  • explosive when mixed with air
  • storage is dangerous
  • making the hydrogen fuel requires energy

chemistry (11 decks)

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