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Chemistry UNIT 2 > The Waffle > Flashcards

The Waffle Flashcards

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1
Q

Equation and benefits of high percentage yield

A

actual amount of product in mol/ theoretical amount of product in mol x100%

reduces waste of starting materials
increases sustainability
very efficient conversion from reactant to product

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2
Q

Equation and benefits of high atom economy

A

molecular mass of desired product/ sum of molecular masses of all products

cheaper
makes less harmful products
reduces amount of waste products
efficient conversion of reactant to desired product
high sustainability
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3
Q

Fractional distillation: what it does and what the products can be used for

A 
separates hydrocarbons from crude oil as fractions
fractions have different boiling points
Usage:
fuels
processing into petrochemicals
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4
Q

Usage of combustion of alkanes

A

fuels in industry
in the home
in transport

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5
Q

Potential dangers of incomplete combustion

A

carbon monoxide is toxic- produced in incomplete combustion of fuels due to limited oxygen supply (in home/ car use)

CO binds irreversibly with haemoglobin in red blood cells, limiting the body’s oxygen supply, leading to oxygen starvation (eventually death)

We should develop ways of ensuring all CO is oxidised to CO2.

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6
Q

Evaluate catalytic cracking

A

obtains more useful alkanes for fuels
shorter so more efficient combustion
short chained alkenes for polymer production

many different chain-lengths obtained as Carbon-Carbon bonds can break anywhere in the chain

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7
Q

Why does the petroleum industry process straight-chained hydrocarbons into branched alkanes and cyclic hydrocarbons

A

to promote efficient combustion

increase octane number (cyclic)

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8
Q

Evaluate the use of fossil fuels for providing energy

A

Increased CO2 levels from processing hydrocarbons and combustion of fossil fuels
leads to global warming and climate change
non renewable resource- crude oil

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9
Q

Evaluate the use of raw materials for providing energy (and name the materials)

A

alcohols and biodiesel produced from plant-based fuels
Bio-fuels produce less CO2 overall
renewable
Plants are a renewable resource
more sustainable
Allows crude oil to be used to make petrochemicals rather than petrol
Allows fossil fuels to be used as a feedstock for organic compounds
No risk of large scale pollution from fossil fuel exploitation

Less food crops may be grown
Deforestation to provide land
reduces fertility of soils
energy needed for processing biofuel makes CO2

Bio-fuels are carbon neutral due to photosynthesis taking up CO2 so net CO2 production is less
Desirability of renewable fuels by ‘rich’ countries may lead to problems of food supply for countries supplying the ‘crops for fuel’.

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10
Q

Limitations of radical substitution in synthesis

A

further substitution forms a mixture of products
low atom economy
harmful products
mixture of products hard to separate

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11
Q

Examples of polymers and their uses

A

H2C=CHCl (chloroethene-> poly(chloroethene) or PVC for water pipes, window frames
F2C=CF2 makes poly(tetrafluoroethene) of PTFE for cable insulation, non-stick domestic utensils

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12
Q

Processing waste polymers

A

Separation into types and recycling (i.e. PTFE)
(need for separation due to recycling a mixture of polymers would produce an inferior plastic product)
Combustion for energy production
(incineration but some plastics produce toxic waste products (PVC produces HCl) so need gas scrubbers to neutralise e.g. using an alkali to react with fumes
Use as feedstock for cracking in the production of plastics and other chemicals

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13
Q

Biodegradable and compostable polymers

A

contain an active functional group that can be attacked by bacteria.
Promising candidates are based on the polymerisation of isoprene, which is the monomer from which rubber is made. (2-methyl-1,3-butadiene)
Also maize and starch used to make polymers biodegradable.
Compostable means the polymer breaks down at the same rate as compost.

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14
Q

Benefits of processing alkenes to produce polymers and plastics

A

Improved consumer health and safety (packaging, containers)
removes the need for incineration
not wasting finite crude oil resource making new polymers

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15
Q

Drawbacks of waste polymers

A

Uses up valuable land in landfill sites
CO2 produced in incineration, global warming

Increased political and social desire to reduce plastic waste, to recycle or to use for energy production

Development of new degradable plastics produced form renewable resources (oil and plant based products, maize and starch)

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16
Q

Uses of ethanol and methanol

A

Use of ethanol
alcoholic drinks
solvent in the form of methylated spirits

Use of methanol
petrol additive to improve combustion
feedstock in producing organic chemicals

17
Q

EVALUATE DIFFERENT METHODS OF PRODUCING ALCOHOLS

A

NEED TO DO THIS!

18
Q

The story of CFCs, why they were first developed, and then what happened…

A 
CFCs were developed as 
aerosol propellants
refrigerants
air-conditioning
because of their low reactivity, volatility and non-toxicity

Scientists discovered that CFCs caused environmental damage to the ozone layer
Provided important evidence which enabled international action to be taken to reduce and phase out CFC use
Subsequently led to development of ozone-friendly alternative and natural repair of the ozone layer

19
Q

Green chemistry’s role in solving CFC problems

A

It attempts to minimise damage to the environment by promoting biodegradable alternatives to CFCs such as
hydrocarbons and HCFCs
CO2 as a blowing agent for expanded polymers (polystyrene)

20
Q

EVALUATE THE USE OF HCFCs

A

NEED TO DO THIS 2

21
Q

Uses of infrared spectroscopy and mass spectrometry

A

IR: modern breathalysers measure ethanol in the breath by analysis, monitoring air pollution as spectra can identify absorptions of functional groups of pollutants
Mass spec: identifying elements i.e. in the Mars space probe, monitoring levels of environmental pollution, such as lead

22
Q

Catalysts usage and evaluation

A
  • speeds up a reaction without being consumed by the overall reaction
  • affects conditions needed, often requiring lower temperatures and reducing energy demand and CO2 emissions from burning of fossil fuels
  • enables different reactions to be used, with better atom economy and with reduced waste
  • are often enzymes, generating very specific products, and operating effectively close to room temperatures and pressures
  • have great economic importance, eg iron in ammonia production, Ziegler-Natta catalyst in poly(ethene) production, platinum/palladium/rhodium in catalytic converters
  • implications for their disposal (toxicity) but benefits in terms of possible lower production costs

the presence of a catalyst allows a reaction to proceed via a different route with a lower activation energy, giving rise to an increased reaction rate

23
Q

The importance in the chemical industry of a compromise between chemical equilibrium and reaction rate

A

high rate (high temperature and pressure vs expense and danger)

a position of equilibrium thats closer to your desired product so better yield (depends on exo/endothermic and molecules on each side of reaction).

24
Q

The Greenhouse Effect of a given gas depends on its

A

atmospheric concentration
ability to absorb IR radiation
residence time in atmosphere

25
Q

Why is it important to control global warming?

A

melting of polar ice cap
low-lying land floods
severe droughts in some areas

26
Q

What are chemists’ roles in minimising climate change resulting from global warming?

A

-provide scientific evidence to governments to verify that global warming is taking place
-collecting data to confirm it, monitoring changes, modelling the potential damage
-investigating solutions such as carbon capture and storage, CSS, ie the removal of waste CO2 as a liquid injected deep in the oceans
storage in deep geological formations
by reaction with metal oxides to form stable carbonate minerals
-monitoring progress against initiatives such as the Kyoto protocol

27
Q

How is the maintenance of the ozone essential for life on Earth

A

Ozone absorbs harmful ultraviolet radiation (UV-B and UV-C which causes skin cancer and sunburn)
Low lying ozone is toxic?

28
Q

What substances may catalyse the breakdown of ozone, and where may these come from?

A

CFCs from refrigerants etc
NOx from thunderstorms or aircraft or internal combustion engines which reach high temp with sufficient energy for N and O from air to react
CO from internal combustion engines incomplete combustion

29
Q

Problems associated with CFCs, NOx and CO?

A

environmental concerns from their toxicity
contribution to low-level ozone
photochemical smog

30
Q

Catalytic converter reaction

A

Catalytic converter decreases CO and NO emissions from internal combustion engines
Adsorption of CO and NO to the catalyst surface (must be weak enough for adsorption and desorption but strong enough to weaken bonds and allow reaction)
Chemical reaction
Desorption of CO2 and N2 from the catalyst surface

31
Q

Principles of chemical sustainability

A
  • Using industrial processes that reduce/eliminate hazardous chemicals, and which involve using fewer chemicals
  • Designing processes with a high atom economy that minimise the production of waste materials
  • Using renewable resources such as plant-based substances
  • Seeking alternative energy sources such as solar energy, rather than consuming finite resources such as fossil fuels that will eventually be exhausted
  • Ensuring that any waste products produced are non-toxic, and can be recycled or biodegraded by being broken down into harmless substances in the environment
32
Q

Importance of establishing international cooperation to promote reduction of pollution levels

A

all countries contribute towards pollution
scientists can share ideas
scientists can warn governments of risk
world-wide legislation can be introduced
monitoring of pollution in other countries
one country can’t control pollution unless all do
richer countries can help poorer countries introduce pollution controls

33
Q

Discuss issues of sustainability based on international cooperation, side-effects of trying to do good and principles of sustainability

A

Not always feasible to use different products in reactions or break down toxic products.
Balance between yield and rate.
Detrimental side effects of trying to be sustainable (e.g. biofuel using land) may outweigh the benefits. Also ethics.
Full international cooperation is often unlikely (e.g. China not a part of Kyoto)

Chemistry UNIT 2 (5 decks)

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