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Chemistry IGCSE > Chemical Energetics > Flashcards

Chemical Energetics Flashcards

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1
Q

What is an exothermic reaction?

A

Reaction in which energy is given out to surroundings

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2
Q

Give examples of exothermic reactions

A

Combustion of fuels
Reaction of acids and metals
Neutralisation

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3
Q

What is an endothermic reaction?

A

Reaction in which energy is taken in from surroundings

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4
Q

Give examples of endothermic reactions

A

Photosynthesis
Thermal decomposition of carbonates
Electrolysis

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5
Q

What is endothermic?

A

bond breaking positive change in temperature value is positive

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6
Q

What is exothermic?

A

Bond forming negative change in temperature value is negative

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7
Q

How can you calculate the energy of a reaction

A
  1. Add together all bond energies for all the bonds in reactants- energy in
  2. Add together all bond energies for all the bonds in products- energy out
  3. Calculate the energy change by energy in- energy out
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8
Q

What is the equation for energy change?

A

Energy taken in - Energy given out

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9
Q

What is a fuel?

A

A substance which releases energy when burned

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10
Q

What does a fuel release?

A

Carbon dioxide and water

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11
Q

How can we measure the efficiency of fuels?

A

By a calorimeter

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12
Q

Where is hydrogen used?

A

In rocket engines and in fuel cells to power some car

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13
Q

What are the advantages of fuel cells?

A

Releases more energy/kilogram

It does not pollute

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14
Q

What are the disadvantages of fuel cells?

A

Expensive to produce and requires energy for production process
Difficult to store and move around
Affected by low temps

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15
Q

How does Uranium-235 release energy?

A

Undergoes decay and gives off heat energy

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16
Q

What are the advantages of using Uranium-235?

A

It is clean as it does not release polluting gases

17
Q

What are the disadvantages of using Uranium-235?

A

Nuclear power plants are expensive and radioactive materials may be released by accident

18
Q

How does a hydrogen fuel cell work?

A

Donates electrons at one electrode and oxygen gains electrons at the other electrode

19
Q

What happens at the anode in a fuel cell?

A

2H2 –> 4H+ +4e-

20
Q

What happens at the cathode in a fuel cell?

A

4H+ +02 +4e- –> 2H2O

21
Q

What is the overall reaction in a fuel cell?

A

2H2 + O2 –> 2H2O

Chemistry IGCSE (6 decks)

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