Fuels And Heats Of Reactions Flashcards
Catalyst
A substance that alters the rate of a chemical reaction but is not used up at the end of the reaction.
Rate of reaction
Change in concentration of a reactant (or product) per unit time.
Isomers
Same molecular formula but different structural formulae
Heats of reaction
The heat change in KJ when the numbers of moles stated in the balanced equation react.
Heat of combustion
Heat change (in KJmole^-1) when one mole of a substance is completely burned in excess oxygen.
Hydrocarbon
Made of carbon and hydrogen atoms only.
Heat of formation
Heat change (in KJmole^-1) when one mole of a substance is formed from its elements in their standard states[i.e as found in nature].
Octane number
A measure of the tendency of a fuel to resist auto ignition (or cause) knocking.
Auto ignition
Ignition before the spark is produced.
Homogeneous catalysts
Catalyst and reactants are in the same phase.
Oxygenates
( Any fuel that contains oxygen in its molecules e.g ethanol/ methanol.)
It increases octane number and decreases the amount of pollution produced.
Aliphatic
Consists of chains or carbon atoms
Unsaturated
They contain a double carbon to carbon bond
Aromatic
Has a benzine ring in its structure
Bond energy
The average amount of energy in kJ needed to break one mole of bonds at the Same time
Hess’s law
The heat change for a reaction is the same whether it takes place in one step or many steps
Kilogram calorific value
The heat produced when 1kg of a fuel is completely burned in excess oxygen
Thermochemistry
Study of heat change that accompany chemical reactions
Structural isomer
A compound with the same molecular formula but different structural formula
How could one show that ethane undergoes an addition reaction with bromine water
Bubble ethene gas through bromine water. Brown to colourless- test for unsaturation
Identify the hydrocarbon gas produced by anaerobic bacterial decomposition of either animal waste or vegetation
Methane
Four processes required to increase the octane number
Dehyldrocyclisation, catalytic cracking, isomerisation and adding oxygenates
Major use of kerosene
Aviation fuel
Major use of residue
Taring the road
What occurs during the secondary sewage treatment?
Oxidation and aeration
Name the oil refining process to convert octane into 2,2,4- trimethylpentane
Isomerisation
Give two structural features of hydrocarbons with high octane numbers
Short carbon cycle and cyclic
Use of ethene and ethyne
Ethene: ripening fruit
Ethyne: welding and cutting
Advantages of adding oxygenates, such as ethanol to fuel
It increases the octane number/ less pollution to environment
Isomerisation
The changing to different structures- making it more branched to increase the octane number
Give two ways in which hydrogen gas is produced
Steam reforming
Electrolysis
How to measure heat of combustion
Bomb calorimeter
Why was lead added to fuel and why was it later discontinued?
To increase octane number. It is carcinogenic
What is the nature of chemicals that make up the bulk of crude oil?
Mostly hydrocarbons
Major use of naphtha or light gasoline
Petrol
Fractionation of crude oil
Separations/ splitting components according to size/ by distillation
Two major components of liquid petroleum gas
Propane and butane/ methylpropane
Why is methanethiol added to natural gas and to LPG?
Safety/ detect leaks
Why is processes a b and c carried out
To increase octane rating(value) / reduces knocking/ increase value of products
IPUC names for 4 hydrocarbons (Q6 2018)
Ethylbenzene/ butane/ but-1-ene/ 2,2,4- trimethlypentane
How would you expect the boiling points of petrol and diesel to compare?
Diesel has higher boiling point/ petrol has lower
Molecular formula of third product
C3H6
Use of Methanol
Production of fertilisers/ ammonia /fuel
Why high molecular mass alkanes have high boiling points
More electrons/ stronger intermolecular bonds
Purpose of dehydrocyclisation
Increase octane value / reduces tendency to cause knocking
Oil refining process that converts octane into ethylbenzene
Dehydrocyclisation/ reforming
Oil refining process in which one molecule of alkane w was converted into one molecule of octane and two propane molecules
Catalytic cracking
Knocking
Igniting before spark
Why solubility of ethen in water differs from its solubility in cyclohexane
Water polar/ cyclohexane non-polar /ethene soluble in cyclohexane but insoluble in water
Factors affecting octane number
Chain length: shorter is higher
Degree of Branching: more branched is higher
Cyclic structure: cylic is higher than chain
Steam reforming equation
CH4 +H2O = CO + 3H2
