C2 Flashcards
(118 cards)
1
Q
What do molecular formulae indicate?
A
They indicate the number and type of each atom present in a molecule.
2
Q
What is the molecular formula of butane?
A
C4H10
3
Q
What does the molecular formula C3H6 represent?
A
Propene
4
Q
What is the displayed formula of phenol?
A
C6H6O
5
Q
What do displayed formulae show?
A
All the bonds present in a molecule.
6
Q
What is the structural formula of butane?
A
C4H10
7
Q
What is the structural formula of 2-methylbutane?
A
CH3CH(CH3)CH2CH3
8
Q
What do structural formulae show?
A
How all the atoms are arranged.
9
Q
What is the purpose of brackets in structural formulae?
A
To show branching groups off the main carbon chain.
10
Q
What is the skeletal formula of pentane?
A
A simplified line representation of the carbon chain.
11
Q
In skeletal formulae, what do the ‘end of the line’ and ‘corners’ represent?
A
A carbon atom.
12
Q
What is a key advantage of using skeletal formulae?
A
They save time as they do not require drawing all hydrogen atoms.
13
Q
What do 3D representations of formulae use to indicate 3-D structure?
A
Dashes and wedges.
14
Q
What does a wedge indicate in a 3D representation?
A
A bond facing towards you.
15
Q
What does a dashed bond indicate in a 3D representation?
A
A bond facing away from you.
16
Q
Fill in the blank: The hydrocarbon octane has the structural formula _______.
A
C8H18
17
Q
What is the general formula for alkanes?
A
CH2n+2
18
Q
What are straight chain alkanes?
A
Alkanes with a single chain of carbon atoms
19
Q
Give an example of a straight chain alkane.
A
Hexane (C6H14)
20
Q
What bonds are formed between carbons and hydrogens in alkanes?
A
Sigma (σ) bonds
21
Q
What are the carbon orbitals involved in bonding in alkanes called?
A
sp³ hybrid orbitals
22
Q
What is hybridisation in the context of alkanes?
A
The rearrangement of the 2s orbital and three 2p orbitals in carbon’s outer shell into four identical orbitals
23
Q
How does the boiling point of straight chain alkanes change with the carbon chain length?
A
The longer the carbon chain, the higher the boiling point
24
Q
What are branched alkanes?
A
Alkanes with one or more carbon atoms attached to a carbon in the main chain
25
Give an example of a branched alkane.
2-methylpentane
26
What are cyclic alkanes?
Alkanes with carbon atoms joined together in a ring
27
Give an example of a cyclic alkane.
Cyclohexane (C6H12)
28
What are structural isomers?
Molecules with the same molecular formula but different structural formulas
29
How many structural isomers exist for C5H12?
Three
30
List the three isomers of C5H12.
* Pentane
* 2-methylbutane
* Dimethylpropane
31
What can differ between structural isomers despite having similar chemical properties?
Physical properties, such as boiling points
32
Fill in the blank: The longer carbon chains have stronger _______ forces.
London
33
True or False: The electron density of larger electron clouds fluctuates less readily than that of smaller clouds.
False
34
What is the boiling point range of kerosene?
250-350 °C
35
What is the boiling point range of diesel?
250-350 °C
36
True or False: The boiling point ranges of diesel and kerosene do not overlap.
False
37
What is the general formula for alkenes?
C_nH_{2n}
## Footnote
Alkenes are a series of hydrocarbons characterized by the presence of at least one carbon-carbon double bond.
38
What type of bonds are formed between carbons and hydrogens in alkenes?
Sigma (σ) bonds
## Footnote
Sigma bonds are formed from the overlap of orbitals in alkenes.
39
What type of hybrid orbitals are involved in the bonding of alkenes?
sp² hybrid orbitals
## Footnote
These orbitals are formed by the rearrangement of the 2s and two of the 2p orbitals in carbon's outer shell.
40
What type of bond is formed by the sideways overlap of p orbitals in alkenes?
Pi (π) bond
## Footnote
The pi bond results from the sideways overlap of remaining p orbitals.
41
What is stereoisomerism in alkenes?
Compounds with the same structural formula but different arrangement in space
## Footnote
Stereoisomers arise due to restricted rotation about the carbon-carbon double bond.
42
How does the pi bond affect rotation around the double bond in alkenes?
It restricts rotation
## Footnote
This locking in position of groups attached to the carbons leads to the formation of stereoisomers.
43
What is the effect of high electron density in alkenes?
Attracts electrophiles
## Footnote
Electron deficient species are attracted to and often react with the double bond in addition reactions.
44
How do the strength and length of double carbon-carbon bonds in hydrocarbons compare to single bonds?
Shorter and stronger
## Footnote
The greater attraction between the nucleus and shared pairs of electrons makes double bonds stronger, but they are not twice as strong due to less effective p orbital overlap.
45
What is the structure of benzene, C6H6, in terms of carbon-carbon bonds?
All carbon-carbon bonds are equivalent length and strength
## Footnote
The delocalization of electrons in p-orbitals results in equal bond lengths and strengths.
46
Fill in the blank: The chemical industry uses hydrocarbons as _______.
starting materials
## Footnote
Hydrocarbons serve as fundamental building blocks in various chemical processes.
47
What is the purpose of a systematic approach to naming hydrocarbons?
To ensure all scientists have a consistent approach to naming.
48
What is the first step in the IUPAC naming rules for hydrocarbons?
Find the longest unbranched chain of carbon atoms.
49
What do prefixes in the name of hydrocarbons indicate?
They are added in front of the stem to indicate side chains.
50
What determines the suffix in the name of a hydrocarbon?
The type of compound, such as alkanes or alkenes.
51
What is a key rule for numbering carbon chains in hydrocarbons?
Count in the direction that gives the lowest possible numbers.
52
How are side chains or functional groups numbered in hydrocarbons?
Number the position of any side chains or functional groups other than alkanes, if necessary.
53
What is the name of the compound with the structure CH3-CH(CH3)-CH2-CH3?
2-methylbutane.
54
What is the stem of the name for a hydrocarbon with five carbons?
pent-.
55
In the name 2,3-dimethylpentane, what does 'di' indicate?
Two methyl groups.
56
What suffix is used for an alkene?
-ene.
57
How is the position of a double bond indicated in the name of a hydrocarbon?
Using the lowest numbered carbon in the double bond.
58
What is the name of the compound with the structure CH3-CH2-CH(CH3)-CH2-CH3?
4-ethyl-3-methyloctane.
59
True or False: The suffix for alkanes is -ene.
False.
60
Fill in the blank: The compound named 4-ethyl-3-methyloctane has a longest unbranched chain of _______ carbons.
eight.
61
What are the two types of hydrocarbons mentioned in the text?
* Alkanes
* Alkenes
62
What is the significance of the order of different side chains in a hydrocarbon name?
Different side chains go in alphabetical order.
63
What is the name of a hydrocarbon with five carbons and a double bond at the first carbon?
pent-1-ene.
64
What are the most important reactions of alkanes?
Combustion and the reaction with halogens
65
What do vehicles burn as fuel?
Hydrocarbon fuels such as petrol or diesel
66
What is the first step in writing combustion equations?
Write the formulae of all the reactants and products
67
How do you balance carbon atoms in combustion equations?
Using carbon dioxide molecules
68
How do you balance hydrogen atoms in combustion equations?
Using water molecules
69
How are oxygen atoms balanced in combustion equations?
Using halves as oxygen is diatomic
70
What is the complete combustion equation for octane?
C3H18(l) + 12302(9) → 8C02(9) + 9H2O(1)
71
What type of hydrocarbons does petrol contain?
Hydrocarbons with 4-12 carbons
72
What type of hydrocarbons does diesel contain?
Hydrocarbons with 8-21 carbons
73
What does complete combustion produce?
CO2 and H2O
74
What does incomplete combustion produce?
CO and C
75
What is the reaction with halogens called?
Free radical substitution
76
What is the first stage in the mechanism of free radical substitution?
Initiation - homolytic bond fission of a halogen
77
What is homolytic bond fission?
When a bond breaks and each fragment retains one electron from the bond pair
78
What occurs during the propagation stage of free radical substitution?
One free radical reacts and forms a different free radical
79
What occurs during the termination stage of free radical substitution?
Combination of any two free radicals to form a stable product
80
What is the initiation equation for the reaction of ethane with bromine?
Br2 → 2Br°
81
What is the propagation equation for the reaction of ethane with bromine?
C2H6 + Br° → °C2H5 + HBr
82
What is the termination equation for the reaction of ethane with bromine?
2Br° → Br2
83
What can happen to C2H5Br during further reactions?
It may collide with a bromine free radical and form a new radical
84
What is a free radical?
A reactive atom or group of atoms that contains an unpaired electron
85
What is one consequence of free radical substitution reactions?
They produce several products and are difficult to control
86
What is the result of the reaction CH2Br + Br° during propagation?
°C2H4Br + HBr
87
What is the balanced equation for the incomplete combustion of C16H34?
C16H34 + O2 → CO + H2O
88
What do MOT tests check for in car emissions?
Carbon monoxide levels
89
What type of reactions do most alkenes undergo?
Addition reactions
## Footnote
Two reactants combine to form one product.
90
What is the nature of the C=C bond in alkenes?
Electron-rich and susceptible to attack by electrophiles
## Footnote
The C=C bond attracts electrophiles due to its high electron density.
91
Define electrophiles.
Species that can accept a pair of electrons
## Footnote
Electrophiles can be positive ions or polar molecules with partial charges.
92
What can induce a dipole in a species near a C=C bond?
The high electron density of the C=C double bond
## Footnote
This allows some neutral species to become electrophiles.
93
What is the role of a curly arrow in addition reaction mechanisms?
Shows the direction in which a pair of electrons moves
## Footnote
Curly arrows illustrate electron movement during the reaction.
94
What is formed after the carbocation in the addition reaction mechanism?
A product forms
## Footnote
The mechanism typically involves the formation of a carbocation intermediate.
95
What is a carbocation?
An intermediate with a positively charged carbon
## Footnote
Carbocations are often unstable and influence product formation.
96
What distinguishes symmetric alkenes from asymmetric alkenes?
Symmetric alkenes have the same groups on either side of the C=C bond; asymmetric alkenes do not
## Footnote
An example of a symmetric alkene is ethene.
97
What happens when asymmetric alkenes react with asymmetric electrophiles?
More than one product forms
## Footnote
The major product is typically the more stable carbocation intermediate.
98
What is the major product when propene reacts with HBr?
2-bromopropane
## Footnote
The major product forms from a more stable carbocation.
99
What stabilizes the carbocation intermediate in the reaction of propene?
The two CH groups attached to the positive carbon
## Footnote
These groups push electrons toward the positive carbon, stabilizing the carbocation.
100
What is the structure of but-1-ene?
CH2=CHCH2CH3
## Footnote
But-1-ene is used in the manufacture of adhesives.
101
Fill in the blank: The major product formed in the reaction of but-1-ene with hydrogen chloride, HCl, is _______.
2-chlorobutane
102
What is addition polymerisation?
The joining together of many alkene monomers to form a saturated molecule called a polymer
## Footnote
For example, ethene can form poly(ethene)
103
What is cracking of alkanes?
The process where larger hydrocarbons with lower commercial demand are broken down by thermal decomposition into smaller, higher demand alkanes and alkenes
104
What is the chemical equation for the polymerisation of ethene?
nCH2=CH2 → (CH2-CH2)n
105
What initiates the formation of free radicals in addition polymerisation?
An initiation step, often by reaction with an oxygen or peroxide catalyst
106
What occurs during the propagation steps of addition polymerisation?
Free radicals react with a monomer forming another free radical with a longer carbon chain
107
What is the termination step in addition polymerisation?
Two long free radicals combine to form the polymer
108
What is the reaction for the hydration of ethene?
C2H4(g) + H2O(g) → C2H5OH(l)
109
What conditions are used for the hydration of ethene?
500K with a phosphoric acid catalyst and a pressure of around 60 atm
110
What is the impact of higher temperatures on the yield of hydrated ethene?
Higher temperatures produce a lower yield
111
What is polystyrene used for?
Insulation and packaging
112
What is the equation for the cracking of decane?
C10H22(l) → C8H18(l) + C2H4(g)
113
What is an example of cracking in industry?
Using diesel fractions (C14-20) cracked with heat and a zeolite catalyst
114
What are the major products from the industrial cracking of diesel?
* Ethene
* Propene
* Petrol
115
What is the relationship between alkane chain length and commercial use in combustion?
Shorter hydrocarbons can be liquefied and stored; longer hydrocarbons are used in fuels like diesel and kerosene
116
What are some issues associated with hydrocarbon use?
* Crude oil is finite
* Polymers are difficult to dispose of
* Combustion produces pollutants
117
True or False: Combustion of hydrocarbons produces solid particulates.
True
118
Fill in the blank: The main source of hydrocarbons is _______.
crude oil
