developing fuels
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what is the ideal gas equation, and what does each letter represent?
pV= nRT • p is pressure in Pa • V is volume in m3 • R is ideal gas equation • n is moles • T is temperature in Kelvin
describe procedure to measure gas volume
• attach gas syringe to the opening of a reaction vessel - when there is no further change in volume, reaction has ended
define enthalpy change
the heat energy which is transferred in a reaction at constant pressure
is bond breaking exothermic or endothermic?
endothermic; energy is required to break bonds
what is an average bond enthalpy?
the energy needed to break one mole of bonds in the gas phase, averaged over many different compounds
why might an average bond enthalpy differ from an experimentally calculated value?
• experimental value might be for a compound not in gaseous phase • experimental value is for a specific compounds whereas average bond enthalpy is not
what is bond length?
the distance between two nuclei where repulsive and attractive forces balance
what has a higher bond enthalpy, a short bond or a long one?
short
what are the products of cracking?
an alkene and an alkane
outline the steps of heterogeneous catalysis
1) reactant molecules arrive at the surface and adsorb to it 2) bonds between the reactants are weakened and break up, forming radicals 3) radicals combine to form products, which desorb from the catalyst
what are the conditions for cracking?
pass hydrocarbon vapour over a heated solid catalyst
what is a sigma bond?
a bond formed when two orbitals overlap in a straight line, very strong due to high electron density
what is a double bond constructed from?
a sigma bond and a pi bond
what is a pi bond?
formed when two orbitals overlap sideways
How do you convert an alkene into an alcohol?
-react with water and cold conc H2SO4 catalyst
How is ethanol manufactured from ethene?
300 degrees, 60 atm, solid phosphoric(V) acid catalyst
name the conditions and a catalyst which could be used in the reaction between hydrogen and an alkene to form an alkane
Nickel catalyst with heat and pressure, or Platinum at room temperature and pressure
how do stereoisomers form?
lack of free rotation around the double bond and different groups on each carbon