2. developing fuels

gas volume

gas volume

same for any one mole at room temperature and pressure

number of moles

= volume in dm3 ÷ 24dm3

room temperature and pressure

298k or 25 ˚c

100 kPa

ideal gas equation

pV = nRT

p = pressure (Pa), V = volume (m3), n = moles, R = gas constant , t = temperature (K)

pV÷RT =

moles, rearranged equation of pV = nRT

gas syringe

used to measure gas volume produced

enthalpy change

∆h is the heat energy transferred in reaction at constant pressure, kJ mol -1

exothermic

gives out energy ∆H is negative, typically oxidation like combustion

endothermic

absorbs energy ∆H is positive eg thermal decomposition or photosynthesis

breaking bonds

energy is required so endothermic ∆H positive

forming bonds

energy released so is exothermic ∆H negative

average bond enthalpies

used to calculate enthalpy changes, for each individual bond , energy needed to break one mole of bonds in gas phase, averaged over many compounds

enthalpy change of reaction

energy absorbed to break bonds - energy released in making bonds

short bond length

means theres a higher bond enthalpy due to there been high attraction between atoms

balanced forces

relation between repulsion between nuclei / electrons and attraction between nuclei and electrons are…

standard enthalpy change of reaction

∆rHø, when as reaction occurs in molar quantities shown in equation

standard enthalpy change of formation

∆fHø, when 1 mole of compound is from formed from its elements in standard states under standard condition

standard enthalpy change of combustion

∆cHø, when 1 mole of substance is completely burnt in oxygen under standard conditions

hess law

total enthalpy change of a reaction is always the same regardless of the route taken

enthalpy of reaction

= enthalpy of formation (products) - enthalpy of formation (reactants)

drawn with elements going to reactants and products

enthalpy of formation

= enthalpy of combustion (products) - enthalpy of combustion (reactants)

drawn with products and reactants going to products of combustion

reactant enthalpy

bond enthalpy (reactants) - bond enthalpy (products)

endothermic reaction

enthalpy of reaction increases, with products ending with more energy than reactants started with

exothermic reaction

enthalpy of reaction decreases, with products ending with less energy than reactants started with

enthalpy level digram

a diagram showing reactants, intermediates and products allowing you to see different routes and activation energy

calorimetry

used to determine energy given out or absorbed by a reaction by measuring temperature change of water

standard enthalpy change of neutralisation

enthalpy change when an acid and and alkali react to form 1 mole of water

calorimetry of a flammable liquid

burn a amount of liquid and heat water, record the temperature change and the mass of water

calorimetry of a solution

add a known volume of acid alkali to a insulated container record the start and end temperature and mass

calculate enthalpy change kJ mol-1

q = mc∆T

q - enthalpy change

m - mass of water or solution

c - specific heat capacity of water

∆T - change in temp of water or solution

cause of error in calorimetry

heat loss- shield

incomplete combustion

evaporation

flame distance

catalysts

increases rate of reaction by providing an alternative pathway with an lower activation energy, without been used by

haber process

uses an iron catalyst

cracking

splitting of a long chain hydrocarbon in to smaller hydrocarbons using using a catalyst to reduce the temp needed to 450˚c

heterogeneous catalyst

catalysts that are in a different physical state as reactants

heterogeneous catalysts process

reactants adsorb to catalyst surface

bond are weakened so break (forms radicals)

new bonds made and desorb

adsorption

process of a reactant bonding just enough to catalyst surface that bonds can be easily broken and released

catalysts poisons

causes them not to work due to surface been covered eg iron by CO or lead on platinum catalytic converters

alkane

saturated hydrocarbon with general formula CnH2n+2

alkenes

unsaturated hydrocarbon with double bonds, general formula of CnH2n

cycloalkanes

saturated hydrocarbon that forms ring, general formula CnH2n

cyclic alkene

a unsaturated hydrocarbon ring with 2 less H than alkenes, stable due to delocalised structure eg benzene and cyclopentene

aromatic compounds or arenes

names for compounds with benzene rings

alcohols

compounds containing -OH hydroxyl group

electron repulsion

shape is created by electrons trying to be as far aspart as possible

tetrahedral

shape of alkenes with a bond angle of 109.5

trigonal planar

shape around a double bond with a bond angle of 120˚

sigma

type of bond between a single covalent bond between atoms, due to the 2 orbitals overlapping in a straight line

sigma and pi bond

type of bond between a double covalent bond, 1 central bond and 1 caused by the overlap of 2 p orbitals sideways, this second one is weaker than the first

general formula

formula that can describe any member of a family of compounds eg CnH2n+1OH

molecular formula

formula with the actual number of atoms in a molecule eg C2H10O

shortened structural formula

shows the atoms carbon by carbon with attached atoms and functional groups eg CH3CH2OH

structural formula

formula showing how the atoms are arranged with their bonds

skeletal formula

shows the bonds of the carbon chain only with any functional groups

different carbon skeleton

isomers with the carbon chain arranged differently, similar chemical properties but different physical properties

functional group location

the carbon chain is the same but the functional group is attached to a different carbon, different physical properties and may have different chemical properties

different functional groups

same atoms arranged into different functional groups very different physical and chemical properties

double bonds

bonds which atoms cannot freely rotate around causing E/Z isomerism

stereoisomers

molecules with the same shortened structural formula but different arrangement

E/Z isomerism

occurs due to lack of rotation around double bonds and different atoms/groups bonded the the carbons, involves H

opposite sides

E or trans isomer

same side

Z or cis is

cis/trans isomerism

isomerism if no H on both sides

addition polymer

formed when the double bonds in alkens break and bond to each other

hydrogen added

added to change an alkene to an alkane in the presence of a nickel catalyst at 150˚c and high pressure or platinum and room temp and pressure

bromine water

used to test for alkanes as it bonds to the double bond causing a colour change orange to colourless

electrophilic addition

double bonds open up and atoms are added

electrophiles

electron pair acceptors eg positively charged ions or polar molecules (double bond)

electrophilic addition mechanism

1. double bond repels electrons in Br2 polarising it ∂+Br-Br∂-

2. electrons are transferred to one Br from the bond, electrons from the double bond are transferred to the other Br and it bonds

   1. a positively charged carbocation intermediate is formed which Br- bonds to

hydrating alkanes in presence of acid catalyst

produces an alcohol by electrophilic addition

alcohol making process

1. cold conc sulphuric acid reacts with an alkene in electrophilic addition reaction to make an intermediate

   1. add cold water and warm to hydrolyse in to product by removing the SO2 regenerating H2SO4

steam hydration

used to make ethanol by hydrating in steam at 300˚c and 60 atm using solid phosphoric acid catalyst, reversible and low yield 5% but recycles to yield 95%

complete combustion

exothermic reaction of alkane in oxygen produces CO2 and water

green house effect

earth radiates infrared radiation and greenhouse gases absorb some of this in the atmosphere keeping earth warm

incomplete combustion

results in formation of carbon monoxide

carbon monoxide

mainly produced in car engines and poisonous

nitrogen oxides

contribute to smog, formed in high pressure and temp of car engines, reacts with sunlight to form ground level ozone which is an irritant

sulfur dioxide

leads to acid rain, produce when fuel contains it, once in atmosphere it dissolves in moisture forming an acid, which destroys vegetation , corrodes buildings and kills fish in lakes, removed from fuels using calcium oxide

particulates

tiny particles of liquid or solids suspended in air, which can settle in lungs and cause issues, removed with wet scrubbers and filters

fossil fuels

non renewable resources like coal, oil and natural ga

decrease pollution

• change laws

• emissions test, compulsory catalytic converter

• tax fuel

• car share, public transport, bikes

renewable fuels

wind, solar and wave power, expensive and need to be extensive

biofuels- produce CO2 and take up farm land

hydrogen- burnt or fuel cell, energy transporter, difficult to transport(liquified)

energy security

make sure there is enough clean and affordable energy