Describe ways that research chemists are trying to minimise climate change resulting from global warming caused by the release of greenhouse gases.
Provide evidence to governments OR international conferences (e.g. Kyoto) OR reports to United Nations etc Educating society OR writing in journals OR producing documentaries OR writing books OR making posters Monitoring atmospheric changes Develop alternative energy sources One example of an alternative energy source e.g. develop fuel cells OR developing solar power OR fuels that do not produce CO 2 (Develop) more efficient engines for transport OR lean burn engines OR hybrid engines OR electric cars Find uses for carbon dioxide OR named use: e.g. dry cleaning OR making decaffeinated coffee OR blowing agent OR fizzy drinks, etc
What is the equation for working out change in combustion of bond enthalpies?
(Sum of bond enthalpies of bonds broken) - (Sum of bond enthalpies of bonds made)
What is the equation for enthalpy changes of formation?
Change in H = (Sum of enthalpy of formation of products) - ( Sum of the enthalpy of formation of reactants)
What is the equation for calculating enthalpy change of combustion?
Change in H = (Enthalpy of combustion of reactants) - (Enthalpy of combustion of products)
In a reaction, what makes it exothermic?
In an exothermic reaction, the bonds that are formed are stronger than the bonds that are broken.
In a reaction what determines wether it is exothermic?
In an endothermic reacttion, the bonds that are formed are weaker than the bonds that are brocken.
Suggest ways in which the use of catalysts helps chemical companies to make processes more stable.
- Catalyst not used up in reaction
- Reactions take place at low temperatures with lower activation energy so less CO2 emitted into atmoshpere/ fossil fuels last longer.
- Less waste/less hazadrous chemicals.
Identify the two main methods of producing ethanol.
Method 1 - Fermentation of sugars or carbohydrates.
- C6H12O6 ---> 2C2H5OH + 2CO2
Method 2 - Hydration of ethene
- C2H4 + H2O ---> C2H5OH
What is the functional group of the product made from reacting an alcohol with a carboxylic acid?
CFC's were banned a long time ago, suggest why there is still concern about ozone depletion.
- CFC's take a long time to reach the ozone layer/ long residence time.
- CFC's are still being used.
- There are other ozone depleting substances.
Outline ways that waste polymers are processed usefully, rather than just dumped into landfill sites.
- Sort plastics, melt and remould.
- Combustion for energy generation.
- Used for cracking/feedstock for plastics or chemicals.
Outline the stages that take place in a catalystic converter to allow CO to react with NO.
1) CO and NO are adsorbed(onto surface)
2)There is a weakening of the bonds/lowering of activation energy.
3) CO2 and N2 desorbed (from surface).
Outline methods that could be developed to achieve carbon capture and storage.
- Stored deep in the oceans.
- Storage in geological locations or under sea-bed.
- By reaction ( with metal oxides) to form carbonates.
- Piped into disused oil wells.
Write out the standard enthalpy of formation of hexane ( include state symbols ).
6C(s) + 7H2(g) -----> C6H14(l)
Why is it very difficult to determine the standard enthalpy change of formation of hexane directly?
- Many diffirent hydrocarbons would form.
- Activation energy to high.
- Reaction to slow.
What are two benefits of using enzymes to catalyse reactions apart from cost?
- Lower temperature can be used.
- Reduces CO2 emissions (from burning fuels).
Give some uses of methanol.
Methanol is used as a petrol additive and as a solvent, feedstock ( in the manufacture of organic compounds), manufacture of biodiesel, manufacture of esters.
Infrared spectroscopy is used in identifying air pollutants such as NOx in identifyinh what?
- Functional groups
- Match spectrum to known pollutants.
- Concentration/ Abundance of pollutant.
A fermentation process has an atom economy of 51.1% and a percentage yield of 88.6%
1) Give two reasons why it is a good idea to find uses for the carbon dioxide produced.
2) Is it important to have a high percentage yield or a high atom economy in fermentation?
1) - Less waste products/better sustainability/100% atom economy.
- Stops green house gases being emitted.
2) One of two arguments:
Percentage yield: - Increase sustainability.
- To reduce waste from starting materials.
- Cheaper/makes less harmful products/increases sutainability.
- Less by products/ more desired products.
Poly(ethene) is found as a waste plastic in the pacific ocean but poly(ethenol) is not because it slowly dissolves in water.
Why does poly(ethenol) dissolve in water?
- has O-H groups
- poly(ethenol) forms hydrogen bonds with water.
Describe examples of environmental damage that may result from carbon monoxide and hyrogen chloride.
1) CO is a poisonous gas.
2) HCl forms acid rain/ is corrosive.
Outline the methods developed by chemists to reduce environmental damage caused by incineration.
1) Remove HCl by reacting with a base.
2) Ensure complete combustion to avoid making CO.
3) Remove CO2 by CCS.
Explain why it is important to establish international coorperation to reduce pollution levels of waste plastics.
- Idea that atmospheric pollution travels across borders.
- Idea that all countries contribute towards pollution.
- Coorperation means scientists share ideas.
- Richer countries can help poorer countries introduce pollution controls.
- One country cant control pollution unless all countries do.
Ozone in the stratosphere is broken down to make O2 and O.
Describe and explain how the concentration of ozone in the stratosphere is maintained.
O + O2 -----> O3
- Reaction is reversible
- Rate of formation of ozone is the same as the rate of depletion of the ozone.
In the past, hydrogen peroxide was manufactured by reacting barium with ice-cold dilute sulfuric acid.
BaO2 (s) + H2SO4(aq) ----> BaSO4(s) + H2O2(aq)
This method required the disposal of poisonous barium compounds and has low atom economy.
Nowadays, it manufactured like so:
H2 + anthraquinone ----> anthraquinol
O2 + anthraquinol ----> H2O2 + anthraquinone
Explain the advantages of the manufacture of H2O2 frp, hydrogen and oxygen.
1) Oxygen comes from air.
2) No poisonous materials formed, no poisonous materials involved.
3) No waste products/atom economy is 100%
4) Anthraquinone is regenerated/recycled/used again/acts as catalyst.
Some reactions of H2O2 are exothermic.
Use ideas about the enthalpy changes that tke place during bond breaking and bond making to explain why some reactions are exothermic.
Bond breaking absorbs energy and bond making releases energy.
More energy released than absorbed.
When looking at infrared spectrometry for determining an uknown compound, what should you always say?
- Peaks that suggest bonds in the structure.
- Peaks not present which suggest the bonds not in a structure.
Research scientists working the Antartic have measured the concentration of carbon dioxide in the ice. This study has allowed the scientists to estimate the atmosperic concentration of carbon dioxide over many thousands of years.
Do the graphs provide reliable evidence that an increase in atmospheric carbon dioxide concentration will result in global warming?
1) There are times when CO2 has a high concetration and the temperature is also high.
2) It is impossible to measure with certainty the average temperature years ago.
3) There are other factors that may cause the green house effect.
4) There are very few anomalous results.
Fractional distillation is used to seperate useful hydrocarbons found in crude oil.
Explain in terms of intermolecular forces, how fractional distillation.
- The hydrocarbons have different boiling points.
- The larger the molecules the stronger the van der Waals' forces.
The reaction between chlorine and cyclohexane is an example of radical substitution.
State one problem of using this reaction to prepare a sample of chlorocyclohexane.
More than one hydrogen atom is substituted OR further substitution occurs.
Explain why many industrial manufacturing processes use catalysts.
Include in your answer ideas about sustainability, economics and pollution control.
- Enable reactions to occur with less waste/ enable reactions with higher atom economy.
- Enable reactions to happen with less toxic solvents/reactants.
- Reactions can occur at lower temperatures and pressures, which saves energy costs.
-reduce carbon dioxide emissions.
- Enable reactions to occur with more specificity.
A space probe has detected the presence of the element iron on the surface of the planet of Mars.
Outline how a mass spectrum would show the presence of iron.
- Would give m/z peaks around 56
The space probe also detected different isotopes of sulfur on Mars.
- Outline how the mass spectrum would show how many different isotopes of sulfur were present on Mars.
The number of m/z values(around 32).
The relative atomic mass of the sulfur found by the space probe was different from the relative atomic mass of sulfur on Earth.
Different isotopic abundance/Different percentage of each isotope.
Biofuels such as bioethanol and biodiesel are increasingly being used as an alternative to fossil fuels to provide energy.
Describe, with the aid of an equation , how bioethanol is manufactured by fermentation.
C6H12O6 ----> 2C2H5OH + 2CO2
- Uses ofyeast/zymase at 25-37*C.
- Anaerobic/ lack of oxygen.
- Seperate bioethanol by fractional distillation.
What is the general formula for an alkyne?
Many lorries and some cars use diesel powered engines.
Biodiesel is being developed as a substitute for diesel from crude oil.
Biodiesel is a methyl ester of a long chain carboxylic acid. The flow chart shows how it is produced:
plants ---> plant oil ---> long chain carboxylic acids ---> biodiesel
Describe the benefits and disadvantages of changing from diesel to biodiesel.
- Save crude oil/no risk of large scale polluton from exploitation of crude oil.
- Biodiesel is renewable.
- Use of biodiesel is(more) carbon neutral/plants take up the carbon dioxide released during combustion.
- Land not used to grow food crops/ rainforests have to be cut down to provide land/ food prices may rise because less is grown.
A student decides to prepare butan-1-ol by the alkaline hydrolysis of 1-chlorobutane.
Suggest,with reasons, any change in the conditions from those used in the alkaline hydrolysis of 1-iodobutane.
- Use of reflux/heat for more than 20 minutes.
- C-Cl stronger bond than C-I bond.
- heat for longer.
What colour does acidified dichromate solution becomes when it oxidises a primary/secondary alcohol?
Orange to green.
Acidified dichromate is reduced.
H2(g) + Cl2(g) -----> 2HCl(g) ΠH= -184 KJ mol-1
Calculate the bond enthalpy for the H-Cl bond using the information.
Bond: H-H = +436 KJ mol-1
Bond: Cl-Cl = +243 KJ mol-1
When asked for the formula of a molecular ion, what do you always have to add?
The "+" sign because its a positive ion.
Suggest why CF2Cl2 does not hydrolyse in water.
(C–F or C–C l ) bonds need a large amount of energy to break
ALLOW ( the C–F or C–C l ) bonds are strong / bonds have a large bond enthalpy ALLOW the molecule is not polar enough / non-polar molecule is not sufficient ALLOW the activation energy is too high DO NOT ALLOW dissolves IGNORE references to hydrogen bonding
Two reasons that CF2Cl2 was used as an aerosol propellant are that it has low reactivity and will not hydrolyse in water.
State one other reason why CF2Cl2 was developed for use as an aerosol propellant.
volatile OR non-toxic OR non-flammable OR easily vaporised
Many scientists believe that we should use more fuels such as biodiesel or bio-ethanol rather than petrol and diesel.
Suggest one reason why these scientists take this view.
Any one from: Bio-fuels produce less carbon dioxide (overall) OR petrol or diesel produce more carbon dioxide (overall) Bio-fuels are renewable OR petrol and diesel are non- renewable Allows crude oil to be used to make other products OR petrochemicals (rather than petrol) OR Save crude oil OR no risk of large scale pollution from exploitation of crude oil
When C12H26 is cracked, a variety of alkanes and alkenes are formed with different chain lengths.
Explain why a variety of alkanes and alkenes are formed with different chain lengths.
Idea that carbon–carbon bonds can break anywhere
A chemical factory uses 200 tonnes of methane a day. The factory produces 68.4 tonnes of hydrogen per day by reacting methane with steam.
CH4(g) + H2O(g) ⇔ CO(g) + 3H2(g)
Calculate the percentage yield of hydrogen.
Describe how hydrogen can be used in the manufacture of margarine.
Unsaturated (vegetable) oils OR oils containing C=C bonds (reacted with hydrogen) in the presence of a nickel catalyst
Scientists monitor pollutant gases in the atmosphere.
State two modern analytical techniques that scientists can use to monitor environmental pollution.
IR (spectroscopy) Mass spectrometry UV (spectroscopy)
Explain why it is important to establish international cooperation to reduce pollution levels.
Idea that pollution travels (across country) borders OR idea that all countries contribute towards pollution OR Cooperation means that scientists can share ideas OR scientists can warn governments of risk OR world-wide legislation can be introduced OR allows monitoring of pollution in different countries OR richer countries can help poorer countries introduce pollution controls OR One country cannot control pollution unless all countries do
Give two reasons why there are many organic products of the reaction between bromine and ethane.
Any two from: More than one C–H bond can be substituted OR multi- substitution can occur OR more than one substitution can happen Lots of termination steps