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A HL Chemistry 2024/2025 > Reactivity 1.3 > Flashcards

Reactivity 1.3 Flashcards

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1
Q

Combustion reaction (endo/exo)

A

Exothermic

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2
Q

Standard enthalpy of combustion

A

Enthalpy change when one mole of substance in its standard state combusts completely in oxygen under standard conditions

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3
Q

Specific energy of a fuel formula

A

Energy released from the fuel / mass of fuel consumed

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4
Q

Specific energy of a fuel units

A

kJ kg-1

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5
Q

Fossil fuel formation

A

Formed from buried organisms that have undergone reduction under pressure

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6
Q

Main fossil fuels

A

Coal, crude oil, natural gas

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7
Q

Crude oil

A

Mixture of hydrocarbons (mainly alkanes)

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8
Q

Natural gas pros/cons

A
  • Clean, easily transportable, higher specific energy density
  • Global warming, limited lifespan, uneven distribution (fracking)
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9
Q

Oil pros/cons

A
  • Easily transported, convenient, feedstock
  • Global warming/acid rain, limited lifespan, risk of pollution
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10
Q

Coal pros/cons

A
  • Present in large quantities, can be converted to synthetic liquid/gases, energy dense, longer lifespan
  • Global warming/acid rain, not easily transported, dangerous mining, dirty
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11
Q

Greenhouse effect

A

Incoming radiation from the sun is UV/visible, most is absorbed, some reflected as IR. Greenhouses gases absorb some radiated infrared heat and reradiate it to the Earth.

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12
Q

Why do greenhouse gases absorb infrared radiation?

A

Molecules increase their vibrational state when they absorb infrared radiation. Three of their vibrational modes are IR active and the dipole changes as they vibrate.

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13
Q

Which vibrational mode of carbon dioxide does not produce a change in dipole and is IR inactive?

A

Symmetrical stretch as the molecule remains symmetrical.

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14
Q

Which vibrational modes of carbon dioxide produce a change in dipole and are IR active?

A

Asymmetrical stretch and two symmetrical bends

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15
Q

How can you find the CO2 equivalent of a greenhouse gas?

A

By multiplying its 100 year global warming potential (GWP)

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16
Q

Carbon footprint

A

Total amount of greenhouse gases produced during human activities

17
Q

Largest contributing factor of carbon footprint

A

Supply and distribution of goods

18
Q

Photosynthesis process

A

Chlorophyll in plants absorb the energy of sunlight (0.6% of total that reaches earth) and convert water/co2 into glucose (carbohydrates)/ (light to chemical energy)

19
Q

Photosynthesis endo/exo

A

It is endothermic and enthalpy change for every mole of glucose formed is +2816 kJmol

20
Q

How can energy from biomass be obtained?

A

Burned directly

21
Q

How can liquid fuel be obtained from biomass?

A

Fermentation

22
Q

Gasohol

A

Mixture of 10% ethanol and 90% gasoline.

23
Q

Biomass fuel cons/pros

A
  • Renewable, low carbon footprint, safe production
  • Uses up land, may pollute water, remove nutrients from soil, small scale production
24
Q

Hydrogen fuel cell

A

Energy produced during combustion of hydrogen in oxygen to form water is given out as electricity. It can give out a continuous supply of electricity.

25
Q

Hydrogen fuel cell unique to rechargable batteries

A

Do not need an external source of electricity and are non polluting as the only product is water

26
Q

Overall reaction in a hydrogen fuel cell (alkaline and acidic)

A

2H2 (g) + 02 (g) -> 2H20 (l)

27
Q

Anode equation alkaline hydrogen fuel cell

A

H2 + 2OH- -> 2H2O + 2e-

28
Q

Cathode equation alkaline hydrogen fuel cell

A

O2 + 2H2O +4e- -> 4OH-

29
Q

Types of electrochemical cells

A

Voltaic -> redox occur spontaneously (chemical - electrical)
Electrolytic cell -> Electrical energy is used to cause reaction (electrical - chemical)

30
Q

Methanol fuel cell

A

When fuels other than hydrogen can be used in fuel cells to convert chemical energy directly to electrical energy

31
Q

Anode equation acidic hydrogen fuel cell

A

H2 -> 2H+ + 2e-

32
Q

Cathode equation acidic hydrogen fuel cell

A

O2 + 4H+ + 4e- -> 2H2O

33
Q

Anode equation methanol fuel cell

A

CH3OH + H2O -> CO2 + 6H+ + 6e-

34
Q

Cathode equation methanol fuel cell

A

3O2 + 12H+ +12e- -> 6H2O

A HL Chemistry 2024/2025 (18 decks)

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