Developing Fuels

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  • Created by: LBCW0502
  • Created on: 22-12-15 15:12
What is an exothermic reaction?
A reaction that gives out energy and heats the surroundings
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What is an endothermic reaction?
A reaction that takes in energy and cools the surroundings
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What are standard conditions?
Set conditions to allow you to compare enthalpy changes: 25 degrees Celsius, 1 atm pressure, and 1 mol dm^-3 for solutions
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What are standard states?
The physical state of a substance under standard conditions. This may be a pure solid, liquid or gas
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How do you convert from Celsius to Kelvin?
Add 273 to the Celsius reading
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What is the standard enthalpy change of a reaction?
The enthalpy change when molar quantities of reactants as stated in the equation react together under standard conditions
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What type of calorimeter can be used to accurately measure energy changes
A bomb calorimeter
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What is the standard enthalpy change of combustion?
The enthalpy change that occurs when one mole of a substance is burnt completely in oxygen under standard conditions in standard states
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What is the standard enthalpy change of formation?
The enthalpy change when one mole of a compound is formed from its elements under standard conditions in standard states
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What is the standard enthalpy change of neutralisation?
The enthalpy change when one mole of hydrogen ions react with one mole of hydroxide ions to form one mole of water under standard conditions and in solutions containing 1 mol dm^-3
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Why are enthalpy cycles used?
Sometimes the enthalpy change of a direct route cannot be measured (e.g. requires lots of energy) so an indirect route is used to calculate energy changes (e.g. enthalpy change of combustion)
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What is Hess' Law?
The enthalpy change for any chemical reaction is independent of the intermediate stages so long as the conditions for the initial and final route are the same
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What is specific heat capacity?
The amount of energy needed to raise the temperature of 1g of a substance by 1K
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What is the law of conservation?
Energy cannot be destroyed or created
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Which process separates fractions in crude oil?
Fractional distillation
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Why can only carbon form a diverse range of compounds for living things?
Carbon has four outer electrons and the carbon ions formed are too highly charged. Carbon forms covalent bonds in compounds (e.g. chains and rings). This property called catenation leads to the limitless variety of organic compounds possible
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What are aromatic compounds?
Compounds that contain one or more benzene rings
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What are aliphatic compounds?
Compounds that do not contain any benzene rings
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What is a functional group?
Modifiers that are responsible for the characteristic chemical reactions of molecules
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What is the general formula for an alkane?
Cn H(2n+2)
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What is the general formula for alkenes and cycloalkanes?
CnH(2n)
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What is a saturated molecule?
Hydrocarbons containing the maximum number of hydrogen atoms possible, no carbon-carbon double or triple bonds
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What is a homologous series?
A series of compounds in which all members have the same general molecular formula
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Which is a structural isomer?
Different structural formulae have the same molecular formula
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What is energy density?
How much energy you get per kilogram of fuel
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How do you calculate energy density?
Standard enthalpy change of combustion x relative molecular mass (x1000)
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What is a chemical bond?
An electrical attraction between atoms or ions
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What is bond enthalpy?
Energy needed to break one mole of a bond to give separate atoms all in the gaseous state (in kJ per mole)
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What is average bond enthalpy?
The average quantity of energy needed to break a particular bond
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Which bonds have a higher enthalpy?
Double/triple bonds (the higher the bond enthalpy, the shorter the bond - stronger attraction)
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What type of reactions are bond-breaking and bond-making
Bond breaking is endothermic (+) and bond making is exothermic (-)
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Why would the experimental value for bond enthalpy not be the same as the data book value?
The bond enthalpy calculated is not actually the standard value. When using bond enthalpies you have to work in the gaseous state. Also, bond enthalpies are averages from several compounds (toolkit) when there is little information about the compound
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What is cracking?
Any reaction in which a larger molecule is made into smaller molecules
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What is meant by unsaturated?
Any organic compound that has a double (or triple) bond between carbon atoms
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What is formed in a cracking reaction involving alkanes?
Branched alkanes and branched alkenes (or smaller alkanes and cycloalkanes)
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What is formed in a cracking reaction involving cycloalkanes?
Alkenes and branched alkenes
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What is formed in a cracking reaction involving alkenes?
Smaller alkenes
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What is a catalyst?
A substance which speeds up a reaction but can be recovered chemically unchanged at the end (provides an alternative route with a lower activation energy)
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What is catalysis?
The process of speeding up a chemical reaction using a catalyst
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What is a homogeneous catalyst?
A catalyst which is in the same physical state as the reactants
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What is a heterogeneous catalyst?
A catalyst which is in a different physical state as the reactants
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What are the main steps in heterogeneous catalysis?
Reactants molecules adsorbed to surface of catalyst, bonds weaken/break, new bonds form, products diffuse from surface of catalyst
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What is meant by catalyst poison?
A substance that stops a catalyst functioning properly
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What is the advantage of using a catalyst?
Less energy is required, small amounts can be used and catalyst can be regenerated
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What is an electrophile?
A positive ion, or a molecule with a partial positive charge, that will be attracted to a negatively charged region and react by accepting a lone pair of electrons to form a covalent bond
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What is a carbocation?
An ion with a positively charged carbon atom
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What do the arrows mean in electrophilic addition?
Full headed arrow (movement of a pair of electrons), half headed arrow (movement of one electron)
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What is an addition reaction?
A reaction where two or more molecules react to form a single larger molecule
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Name examples of reactions which involve electrophilic addition?
Ethene and bromine, ethene and hydrogen bromide, ethene and water, ethene and hydrogen
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What are the conditions for a hydrogenation reaction?
Nickel catalyst, 150 degrees Celsius and a pressure of 5 atm (or platinum catalyst under standard laboratory conditions)
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What are the conditions for a hydration reaction?
High temperature, high pressure, phosphoric acid adsorbed onto solid silica as a catalyst
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What is a polymer?
A long molecule made up from lots of small molecules called monomers
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What is polymerisation?
Small molecules (monomers) join together to produce long chain polymers (addition polymerisation - one product is produced)
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What is copolymerisation?
More than one type of monomer joins together form a polymer
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What is the ideal gas equation?
PV=nRT
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What is chain isomerism?
Molecules have different arrangements of carbon atoms (different chain lengths formed)
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What is position isomerism?
An atom or group of atoms substituted in a carbon chain or ring (functional groups)
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What is functional group isomerism?
Same molecular formula but different functional groups
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What are the two types of stereoisomerism?
E/Z isomerism and optical isomerism
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What is an E isomer?
Groups are on different sides of the C=C double bond
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What is a Z isomer?
Groups are on the same side of the C=C double bond
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What is photochemical smog?
A photochemical reaction occurs when a molecule absorbs light energy and then undergoes a chemical reaction
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What are the problems with photochemical smog?
Reduces visibility, nose/eye irritation and respiratory problems
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What is the polluting effect of sulphur dioxide?
Produces acid rain (destroys buildings and aquatic life)
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Name 2 examples of biofuels
Ethanol and biodiesel
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What are the advantages of biodiesel?
Made from waste oil, carbon neutral, most diesel vehicles run on pure biodiesel, biodegradable, no sulphur emissions, less pollutants produced
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What are the disadvantages of biodiesel?
Produces more nitrogen oxides than conventional fossil fuels
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What are the advantages of hydrogen as a fuel?
Renewable, can be stored, used to generate electricity, only produces water (carbon dioxide, carbon monoxide, hydrocarbons)
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What are the disadvantages of hydrogen as a fuel?
Production from water depends on use of electricity (fossil fuels), less energy dense than petrol and oxides of nitrogen are still produced
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What can be used to reduce the emission of pollutants (carbon monoxide and unburnt hydrocarbons)
Catalyst to speed up reactions with oxygen (to produce carbon dioxide and water) and nitrogen oxide (to form carbon dioxide and nitrogen)
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Card 2

Front

What is an endothermic reaction?

Back

A reaction that takes in energy and cools the surroundings

Card 3

Front

What are standard conditions?

Back

Preview of the front of card 3

Card 4

Front

What are standard states?

Back

Preview of the front of card 4

Card 5

Front

How do you convert from Celsius to Kelvin?

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Preview of the front of card 5
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