Developing fuels

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All gases take up the sme volume under the same conditions. At room temperature (298k) and pressure (100kPa) what is this volume?
24.0 dm^3
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How can you caluclate the number of moles in a volume of gas?
volume in dm / 24 (if the volume is in cm then you divide by 24,000)
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What is the ideal gas equation?
pV= nRT (p= pressure v=volume (in meteres cubed (1 cm = 1 x 10^-6 and 1 dm = 1 x 10^-3) n=moles r= gas constant (8.314) t= temperature (kelvin))
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How would you measure gas volume?
Attach a gas syringe to the opening of a reaction vessel and measure the amount of gas produced.
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What is an enthalpy change?
ΔH is the heat energy transferred in a reaction when bonds are either broken or made, at constant pressure.
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What is the symbol used for when an enthalpy change was made under standard conditions?
.
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What is an exothermic reaction? Give an example of an exothermic reaction:
A reaction that gives out energy, the ΔH is negative. Oxidation is usually exothermic for example oxidation of glucose in respiration
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What is an endothermic reaction? Give an example:
Reactions that absorb energy. ΔH is positive. Thermal decomposition of calcium carbonate is endothermic
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How can enthalpy changes be calculated using average bond enthalpies?
Enthalpy change = total energy absorbed to break bonds - total energy released in making bonds.
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What is a bond enthalpy?
The energy needed to break a bond or the energy given out when a bond is formed. Stronger bonds have higher bond enthalpies
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What is a bond length?
The distance between the two positive nuclei which is the distance where the attractive and repulsive forces balance each other. The stronger the attraction between the atoms the higher the bond enthalpy, the shorter the bond length.
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What are the different types of enthalpy changes?
Standard enthalpy change of reaction, formation, neutralisation and combustion
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What is standard enthalpy change of reaction? Give the symbol:
Enthalpy change wen the reaction occurs in the molar quantities shown in the chemical equation under standard conditions
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What is standard enthalpy change of formation? Give the symbol:
The enthalpy change when 1 mole of a compound is formed from its elements in their standard states, under standard conditions
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What is standard enthalpy change of combustion? Give the symbol:
The enthalpy change that occurs when 1 mole of a substance is completely burnt in oxygen, under standard conditions
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What does Hess's Law say?
The total enthalpy change of a reaction is always the same, no matter which route is taken
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Give an example of how enthalpy changes can be worked out from enthalpies of formation:
.
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Give an example of how enthalpy changes can be worked out from enthalpies of combustion:
.
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Give an example of how reaction enthalpies can be calculatedusing bond enthalpies:
.
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What is the activation energy (and give the symbol)?
The minimum amount of energy needed to begin breaking reactant bonds and start a reaction
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Draw an enthalpy level diagram for an endothermic reaction:
.
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Draw an enthalpy level diagram for an exothermic reaction:
.
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The les enthalpy a sunbstance the more ... it is
stable
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How can you find out the enthalpy of combustion of a flammable liquid using calorimetry?
1. Burn a fuel 2. It heats the water 3. work out the heat absored by the water using q=mcΔT 4.
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What is standard enthalpy change of neutralisation (give the symbol)
The enthalpy change when an acid and an alkali react together, under standard conditions, to form 1 mole of water
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How can you use calorimetry to calculate an enthalpy change that happens in solution such as neutralisation or displacement?
1. Add a known volume of acid to an insulated container and measure the temperature 2. add a known volume of alkali and record the temp rise 3. work out the heat needed to raise the temp using q=mcΔT
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What do the symbols in this equation mean q=mcΔT?
q= heat lost or gained (joules) m = mass of water c= specific heat capacity of water (4.18)ΔT = the change in temp of the water (k)
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What is a catalyst?
A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy. The catalyst is chemically unchanged at the end of the reaction
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What is catalysis?
Speeding up a chemical reaction by using a catalyst
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What are heterogenous catalysts? Give an example
Catalysts in a different physical state from the reactants. Iron in the haber process (forming ammonia from N2 and H2) and platinum in catalytic converters.
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What do catalytic converters do?
Get rid of harmful gases produced from a car exhaust and convert them into harmless gases like water vapour and nitrogen
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How do reactions happen on a heterogenus catalyst? (part 1 of 2)
1. Solid catalyst prvides a surface 2. reactant molecue arrives at the surface and bonds with the solid catalyst (adsorption) 3. bonds between the reactant's atoms are weakend and break up, forming radicals which get together to make new molcules
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How do reactions happen on a heterogenus catalyst? (part 2 of 2)
4. new molecules detach from the catalyst (desorption
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What are radicals?
atoms or molecules with unpaired electrons
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Give two examples of a catalyst being posined:
1. Carbon monoxide posions the solid iron catalyst in the Haber process 2. lead posions the catalyst in catalytic converters (a problem before we had unleaded petrol)
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Why do heterogenus catalysts often get posioned?
The posion clings to the catalysts surface more strongly than the reactant does so the catalyst is prevented from getting involved in the reaction
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What are alkanes?
Saturated hydrocarbons
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What is the general formula of an alkane?
CnH2n+2
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What is the general formula of a cycloalkane?
CnH2n
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What are alkenes?
Unsaturated hydrocarbons C=C
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What is the general formula of an alkene?
CnH2n
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What is the formula for a benzene ring?
C6H6
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What is the general formula of an alcohol?
CnH2n+1OH
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What are the stem names for the number of carbons 1-10?
meth, eth, prop, but, pent, hex, hept, oct, non, dec
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Draw out this compound: 3-ethyl-2,4-dimethylpentan-2-ol
.
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What are the suffix/prefix of these homologous series: alkane, sid chain in an alkane, alkene, haloalkane, alcohol, cycloalkane, arene
-ane, alkyl-, -ene, chloro/bromo/iodo-, -ol, cyclo- -ane, -benzene
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What shape do single bonded carbon atoms form?
Tetrahedral
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What shape do doube bonded carbon atoms form?
Equilateral triangle - trigonal planar
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What is a sigma bond?
When two orbitals overlap in the space between two atoms, this gves the highhes possible electron density making sigma bonds very strong (it is a single covaent bond)
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A double bond is made up of a sigma and pi bond. What is a pi bond?
Two p orbitals overlap sideways, it is weaker than a sigma bond.
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What are the 3 different types of structural isomers?
1. Different carbon skeleton 2. functional group in a different place 3. different functional groups
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Atoms can rotate around double bonds. True or false?
False
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What are stereoisomers?
Stereoisomers have the same shorterned structural formula but a different arrangement. Due to the lack of rotation around a double bond, alkenes have stereoisomers
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Draw a diagram of a Z isomer
.
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Draw a diagram of a E isomer
.
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E/Z isomers can also be called cis/trans isomers. Which reflects which?
Cis = Z Trans = E
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Alkenes join up to form what?
Addition polymers
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How do alkenes join up to form addition polymers?
The double bonds in alkenes open up in a process called addition polymerisation.
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How woud you add hydorgen to an alkene to produce an alkane?What kind of reaction is this
Ethene will react with hydorgen gas to produce ethane - a nickel catalyst is required and a temp of 150 celcius and a hgh pressure or a platinum catalyst at room temp and pressure. This is an addition reaction
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How do you use bromine water to test for C=C bonds? What kind of reaction is this
When you shake an alkene with orange bromine water, the solution will decolourise - the bromine is bing added across the double bond to form colourless dibromoalkane. This is an example of electrophilic addition
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What is an electrophile? Give some examples
Electron-pair acceptors. Positively charged ions, polar molecules
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Why is the double bond described as nucleophillic?
Because its attracted to places that dont have enough electrons
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Draw a mechanism for an electrophilic addition reaction:
.
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Draw an example of an alkene undergoing addition with a hydroge halide:
.
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How can you make an alcohol using an alkene?
1. React sulfuric acid and an alkene in an electrophilic addition 2. add water and warm the product, its hydrlysed to form an alcohol (sulfuric acid isnt used up as it acts as the catalyst)
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How is ethanol manufacturated by steam hydration?
Ethene can be hydrated by steam at 300 celcius and a pressure of 60. It needs a phosphoric acid catalyst
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What are the products when you burn an alkene completely in oxygen?
Carbon dioxide and water
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Is the combustion of an alkane, alcohol or cycloalkane endothermic or exothermic?
Exothermic (which is why they make great fuels)
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Carbon dioxide is a greenhouse gas, what is the greenhouse effect?
When greenhouse gases absorb the infrared radiation that the earth emits (making the earth warmer)
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If there is not enough oxygen in a combustion reaction what is produced instead of carbon dioxide?
Carbon monoxide
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What is wrong with carbon monoxide?
It is posionous - they are similar to O2 molecules so they can bind to haemoglobin molecules - it is better at binding and so causes internal suffocation
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Unburnt hydrocarbons produce oxides of nitrogen which contribute to what pollutant?
Smog
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What does sulfur dioxide lead to?
Acid rain
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Why are particulates classed as a pollutant?
Tiny particles can settle in lungs and decrease lung function as well as causing cardiovascular problems
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How can sulfur dioxide be removed from power station emissions?
Calcium oxide
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How can particulates be removed from power station emissions and car exhausts?
Wet scrubbers in power stations and filters in exhausts
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What is used to reduce carbon monoxide from car exhausts?
Catayltic converters
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Whatare some renewable fuels?
wind, solar, wave and biofuels
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How can hydrogen gas be used as a fuell source?
It can be burned or used in a fuel cell. It can be obtained from sea water but takes energy to extract it
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Other cards in this set

Card 2

Front

How can you caluclate the number of moles in a volume of gas?

Back

volume in dm / 24 (if the volume is in cm then you divide by 24,000)

Card 3

Front

What is the ideal gas equation?

Back

Preview of the front of card 3

Card 4

Front

How would you measure gas volume?

Back

Preview of the front of card 4

Card 5

Front

What is an enthalpy change?

Back

Preview of the front of card 5
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