Fuels And Heats Of Reactions

Question 1

Catalyst

Answer 1

A substance that alters the rate of a chemical reaction but is not used up at the end of the reaction.

Question 2

Rate of reaction

Answer 2

Change in concentration of a reactant (or product) per unit time.

Question 3

Isomers

Answer 3

Same molecular formula but different structural formulae

Question 4

Heats of reaction

Answer 4

The heat change in KJ when the numbers of moles stated in the balanced equation react.

Question 5

Heat of combustion

Answer 5

Heat change (in KJmole^-1) when one mole of a substance is completely burned in excess oxygen.

Question 6

Hydrocarbon

Answer 6

Made of carbon and hydrogen atoms only.

Question 7

Heat of formation

Answer 7

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].

Question 8

Octane number

Answer 8

A measure of the tendency of a fuel to resist auto ignition (or cause) knocking.

Question 9

Auto ignition

Answer 9

Ignition before the spark is produced.

Question 10

Homogeneous catalysts

Answer 10

Catalyst and reactants are in the same phase.

Question 11

Oxygenates

Answer 11

( Any fuel that contains oxygen in its molecules e.g ethanol/ methanol.)
It increases octane number and decreases the amount of pollution produced.

Question 12

Aliphatic

Answer 12

Consists of chains or carbon atoms

Question 13

Unsaturated

Answer 13

They contain a double carbon to carbon bond

Question 14

Aromatic

Answer 14

Has a benzine ring in its structure

Question 15

Bond energy

Answer 15

The average amount of energy in kJ needed to break one mole of bonds at the Same time

Question 16

Hess’s law

Answer 16

The heat change for a reaction is the same whether it takes place in one step or many steps

Question 17

Kilogram calorific value

Answer 17

The heat produced when 1kg of a fuel is completely burned in excess oxygen

Question 18

Thermochemistry

Answer 18

Study of heat change that accompany chemical reactions

Question 19

Structural isomer

Answer 19

A compound with the same molecular formula but different structural formula

Question 20

How could one show that ethane undergoes an addition reaction with bromine water

Answer 20

Bubble ethene gas through bromine water. Brown to colourless- test for unsaturation

Question 21

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

Answer 21

Methane

Question 22

Four processes required to increase the octane number

Answer 22

Dehyldrocyclisation, catalytic cracking, isomerisation and adding oxygenates

Question 23

Major use of kerosene

Answer 23

Aviation fuel

Question 24

Major use of residue

Answer 24

Taring the road

Question 25

What occurs during the secondary sewage treatment?

Answer 25

Oxidation and aeration

Question 26

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

Answer 26

Isomerisation

Question 27

Give two structural features of hydrocarbons with high octane numbers

Answer 27

Short carbon cycle and cyclic

Question 28

Use of ethene and ethyne

Answer 28

Ethene: ripening fruit Ethyne: welding and cutting

Question 29

Advantages of adding oxygenates, such as ethanol to fuel

Answer 29

It increases the octane number/ less pollution to environment

Question 30

Isomerisation

Answer 30

The changing to different structures- making it more branched to increase the octane number

Question 31

Give two ways in which hydrogen gas is produced

Answer 31

Steam reforming | Electrolysis

Question 32

How to measure heat of combustion

Answer 32

Bomb calorimeter

Question 33

Why was lead added to fuel and why was it later discontinued?

Answer 33

To increase octane number. It is carcinogenic

Question 34

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

Answer 34

Mostly hydrocarbons

Question 35

Major use of naphtha or light gasoline

Answer 35

Petrol

Question 36

Fractionation of crude oil

Answer 36

Separations/ splitting components according to size/ by distillation

Question 37

Two major components of liquid petroleum gas

Answer 37

Propane and butane/ methylpropane

Question 38

Why is methanethiol added to natural gas and to LPG?

Answer 38

Safety/ detect leaks

Question 39

Why is processes a b and c carried out

Answer 39

To increase octane rating(value) / reduces knocking/ increase value of products

Question 40

IPUC names for 4 hydrocarbons (Q6 2018)

Answer 40

Ethylbenzene/ butane/ but-1-ene/ 2,2,4- trimethlypentane

Question 41

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

Answer 41

Diesel has higher boiling point/ petrol has lower

Question 42

Molecular formula of third product

Answer 42

C3H6

Question 43

Use of Methanol

Answer 43

Production of fertilisers/ ammonia /fuel

Question 44

Why high molecular mass alkanes have high boiling points

Answer 44

More electrons/ stronger intermolecular bonds

Question 45

Purpose of dehydrocyclisation

Answer 45

Increase octane value / reduces tendency to cause knocking

Question 46

Oil refining process that converts octane into ethylbenzene

Answer 46

Dehydrocyclisation/ reforming

Question 47

Oil refining process in which one molecule of alkane w was converted into one molecule of octane and two propane molecules

Answer 47

Catalytic cracking

Question 48

Knocking

Answer 48

Igniting before spark

Question 49

Why solubility of ethen in water differs from its solubility in cyclohexane

Answer 49

Water polar/ cyclohexane non-polar /ethene soluble in cyclohexane but insoluble in water

Question 50

Factors affecting octane number

Answer 50

Chain length: shorter is higher Degree of Branching: more branched is higher Cyclic structure: cylic is higher than chain

Question 51

Steam reforming equation

Answer 51

CH4 +H2O = CO + 3H2