Fuel and Heats of Reactions

What is 2,2,4-trimethylpentane's octane number

100

Name the reference hydrocarbon that is the majorncompnent of the 83:17 reference hydrocarbon

2,2,4-trimethylpentane

A Hydrocarbon

A compound that contains hydrogen and carbon only

Define bond energy

Average energy required to break a bond and to separate the atoms into separate atoms in the gaseous state

Give a major use for kerosene

Aviation fuel Home heating

Name the laboratory apparatus used to measure the heats of combustion of fuels and foodstuff

Bomb calorimeter

Name 3 processes carried out in oil refining to modify hydrocarbon structures

Catalytic Cracking Isomeriation Reforming

Name the oil refining process in which one molecule of an alkane was converted into one molecule of octane and two propene molecules

Catalytic cracking

Explain the term isomeriation

Changing to different structures that have the same molecular formula

Define structural isomers

Compounds with same molecular formula but different structural formulas

Write the balance equation for the complete combustion of butane in oxygen

C⁴H¹⁰ + 6½O² -> 4CO² + H²O

Name the oil refining process the converts octane into ethylbenzene Why is it desirable ?

Dehydrocyclisation Improved octane rating Reduces tendency of fuel to cause knocking

How would you expect the boiling points of diesel and petrol to compare ?

Diesel has a higher boiling point Petrol has a lower boiling point

Describe a method by which hydrogen can be obtained from water

Electrolysis

State a disadvantage of hydrogen as a fuel

Explosive Leaks easily

Give a use of methane

Fuel Production of hydrogen

State an advantage of catalytic cracking

Gives useful products Gives products higher octane numbers

Why is methane gas a cause of concern ?

Global warming Enhanced greenhouse gas

State Hess's Law

Heat change for a reaction depends only on initial and final stages

Define heat of combustion

Heat change when 1 molecule of a substance is burned completely in excess oxygen

What are two reference hydrocarbons used to assign octane numbers to fuels ?

Heptane 2,2,4-trimethylpentane

Why are the boiling points of hexane higher then propane ?

Hexane has a higher molecular mass, bigger molecules, more electrons and stronger van der waals forces

Describe how got crude oil is separated into useful substances in an oil refinery

Hot crude oil is introduced at base it fractionating column, heated at the bottom. Vapour moves up the trays. Fractions come off through outlets depending on their boiling points.

What is the nature of chemicals that make up the bulk of crude oil ?

Hydrocarbons

Why is MTBE added to fuel

Increase octane number Prevent auto-ignition

Give two advantages of adding oxygenates such as ethanol to petrol

Increase octane number Reduces knocking

What is the purpose of dehydrocyclisation in oil refining ?

Increase octane rating of a fuel Reduces tendency of fuel to cause knocking

Name the oil refining process which convert octane into 2,2,4-trimethylpentane

Isomerisation

Name the fraction obtained from crude oil that is used for fuel for jet aircraft

Kerosene

Name the substance previously added to fuel and state why it was discontinued

Lead components eg tetraethylled It was toxic Poisons catalytic converters

Name two properties of Hydrogen that made it the fuel of choice for a space shuttle

Light High energy content per kilogram

Define octane number of a fuel

Measure of tendency to auto-ignite

Identify the hydrocarbon gas produced by anaerobic bacterial decomposition of either animal waste or vegetation

Methane

Name the Alkanes

Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10 Pentane C512 Hexane C614 Heptane C716 Octane C8H18 Nonane C9H20 Decane C10H22

What fraction do heptane and methylbenzene occur

Naphtha

Give a major use of light gasoline and naphtha

Petrol Motor fuel

Outline how the heat of combustion came be measured using the bomb calorimeter

Place know amount of substance in bomb calorimeter. Pressurise with oxygen. Place bomb in known quantity of water. Ignite electrically. Find the heat produced using the rise in temperature and the heat capacity.

Name two major components of liquid petroleum

Propane Butane

Give a major use for residue

Roofing Road making

Explain fractionating of crude oil

Separation into components according to molecular mass

What is catalytic cracking ?

Splitting of long chain molecules by the action of heat and catalysts to give short chains

Give two ways hydrogen gas is produced industrially

Steam reforming Dehydrocyclisation

Explain why higher molecular mass alkanes have higher boiling points

Stronger intermolecular bonds and more electrons present to create intermolecular forces

What is meant by auto-ignition in petrol engines ?

Tendency to pre-mature ignitionn

Why is CH³SH (a mercaptan) added to natural gas?

To give it a smell Help detect leaks

Why was tetraethylled discontinued in car engines ?

Toxic to the environment Damages catalytic converters

Fossil fuel

are fuels that were formed by the remains of plants and animals that lived millions of years ago

A saturated compound

is one in which there are only single bonds between the atoms in the molecule eg Alkanes

What is the advantage of adding tetraethylled to petrol ?

to reduce auto-ignition to increase octane number