Chapter 21 Organic Chemistry

Question 1

Saturated compounds

Answer 1

There are only single bonds between the atoms in the molecule

Question 2

Homologous series *(4)

Answer 2

’ a series of compounds of similar chemical properties,
‘ showing gradations in physical properties
‘having a general formula for its members
‘ each member has a similar method of preparation

Question 3

Structural isomers + eg :

Answer 3

Compounds with the same molecular formula but different structural formulas
*eg : butane and methylpropane = C4 H10

Question 4

Methyl group (molecular formula)

Answer 4

C H3

Question 5

Ethyl group (molecular formula)

Answer 5

C2 H5

Question 6

Alliphatic (definition)

Answer 6

Have molecules in chains or rings of carbon atoms

Question 7

Aromatic (definition)

Answer 7

Hydrocarbons with a benzene ring of 6 carbon atoms, where the bonds are intermediate between single and double bonds. /\
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Question 8

Alkanes (formula) / bonds

Answer 8

Cn H 2n +2 / saturated , single bonds

Question 9

Tetrahedral (carbon)

Answer 9

A central atom is located at the center with 4 substituents

Question 10

Propyl group (molecular formula)

Answer 10

C3 H7

Question 11

1st 5 alkanes (list)

Answer 11

Methane, ethane, propane, butane, pentane…

Question 12

(True or false)

Alphabetical order is always followed regardless of the numbering? +eg

Answer 12

True,

Eg= 2 ethyl - 3-methylhexane

Question 13

Alkene (molecular formula) / bonds

Answer 13

Cn H2n / unsaturated, 1 carbon-carbon double bond

Question 14

Unsaturated compound (definition)

Answer 14

Compound contains one or more double or triple bonds between the atoms in the molecule

Question 15

1st 3 alkenes + state

Answer 15

Ethene, propene, butene

State = gas

Question 16

test for unsaturation (1 or 2)

Answer 16

(1) bromine water goes from red to colorless (2) potassium permanganate goes from purple to colorless

Question 17

Alkyne (molecular formula) / bonds

Answer 17

Cn H2n -2 / highly unsaturated , 1 carbon- carbon triple bond

Question 18

1 alkyne (on course)

Answer 18

ethyne

Question 19

3 aromatic hydrocarbons + properties (3)

Answer 19

benzene, methylbenzene ethylbenzene / intermediate bonds, nonpolar (not dissolving in water) Lower molecular mass (liquid at room temp.)

Question 20

process used to separate crude oil into a number of useful parts by heating and separating on the basis of their boiling points

Answer 20

fractional distillation

Question 21

Give uses of the following : 1. refinery gas 2. petrol 3. naphtha 4. kerosene 5. diesel oil 6. lubricating oil 7. fuel oil 8. bitumen

Answer 21

1.= LPG for cooking 2.= petrol for cars 3.= chemicals for the petrochemical industry 4.= central heating 5= cars /buses 6.= lubricating oil /waxes 7.= fuel for ships 8.= for roads and roofing

Question 22

auto ignition (definition)

Answer 22

premature ignition of the petrol -air mixture before normal ignition of the mixture by spark takes place

Question 23

Octane number (definition)

Answer 23

of a fuel is the measure of the tendency of the fuel to resist “knocking”

Question 24

(1.) 2,2 4, trimethylpentane + (2.) heptane ( octane no.)

Answer 24

1= 100 ,,2= 0

Question 25

factors affecting Octane no.

Answer 25

length of chain (the shorter the chain the higher the no.) , degree of branching (the more branched the higher the octane no.) Straight/cyclic chain ( cyclic chain has higher octane no . )

Question 26

4 ways to increase the octane no. of petrol

Answer 26

isomerisation, catalytic cracking , dehydrocyclization, adding oxygenates

Question 27

catalytic cracking

Answer 27

breaking down of long chain hydrocarbons molecules by the action of heat +
catalysts into short - chain molecules

Question 28

2 ways of manufacturing hydrogen gas

Answer 28

steam reforming of natural gas , electrolysis of water

Question 29

heat of reaction (symbol)

Answer 29

/\ H ( delta H)

Question 30

heat of reaction ( definition)

Answer 30

is the heat change when the no. of moles of reactants indicated in the balanced equation for the reaction react completely

Question 31

heat of combustion ( definition)

Answer 31

heat change when 1 mole of the substance is completely burned in excess oxygen

Question 32

Kilogram calorific value ( definition)

Answer 32

is the heat energy produced when 1 kg of the fuel is completely burned in oxygen

Question 33

Bond energy ( definition)

Answer 33

is the average energy required to break 1 mole of a particular covalent bond and to separate the neutral atoms completely from each other

Question 34

heat of neutralisation ( definition)

Answer 34

heat change when 1 mole of H+ ions from an acid reacts

with one mole of OH- ions from a base

Question 35

heat given out (equation)

Answer 35

mass * specific heat capacity * rise in temp. ( MC /\ T)

Question 36

standard state

Answer 36

Standard state normally is room temperature (25°C) and normal atmospheric pressure (14.7 psi).

Question 37

heat of formation

Answer 37

of a compound is the heat change that takes place when 1 mole of a compound in its standard state is formed from its elements in their standard states

Question 38

Hess’s Law

Answer 38

if a chemical reaction takes place in a number of stages the sum of the heat changes in the separate stages is equal to the heat change if the reaction was carried out in one stage

Question 39

Law of conservation of energy

Answer 39

energy cannot be created or destroyed , only converted from one form to another

Question 40

propyl group

Answer 40

C3 H7