Organic Chemistry p67-74 Flashcards
1
Q
What is the general formula for ethene?
A
CnH2n (for all alkenes)
2
Q
What is the Empirical formula for ethene?
A
CH2
3
Q
What is the molecular formula for ethene?
A
C2H4
4
Q
What is the structural formula for ethene?
A
CH2CH2 (remember displayed)
5
Q
What is homologous series?
A
- group of compounds that can all be represented by the same general formula
6
Q
Are alkanes a homologous series?
A
-yes
-only contain carbon and hydrogen atoms
7
Q
What do molecules in a homologous series contain?
A
-contain the same functional group
8
Q
What is a functional group?
A
-group of atoms that determine how a compound typically reacts
-this means compounds in homologous series typically react in similar ways
9
Q
What are the four functional groups of homologous series?
A
- Alcohols
-Alkenes
-Carboxylic Acid
-Esters
10
Q
What is the stem if the number of carbons is 1?
A
meth-
11
Q
What is the stem if the number of carbons is 2?
A
eth-
12
Q
What is the stem if the number of carbons is 3?
A
prop-
13
Q
What is the stem if the number of carbons is 4?
A
but-
14
Q
What is the stem if the number of carbons is 5?
A
pent-
15
Q
What is the stem if the number of carbons is 6?
A
hex-
16
Q
When are two molecules isomers of each other?
A
- when they have the same molecular formula but the atoms are arranged differently
17
Q
Why can you look for differently shaped carbon chains when spotting Isomers?
A
-carbons could be arranged differently
-e.g as a straight chain or branched (one of the carbons being bonded to more than two carbons) in different ways
18
Q
Why will the physical properties of an isomer be different?
A
- because of the change in shape of the molecule
19
Q
Why can you have functional groups in different places when spotting an Isomer?
A
- arrangement of carbon atoms could be the same
-isomers could have the same functional group
-but the functional group could be attached to a different carbon atom
20
Q
Why can you have different functional groups when spotting an Isomer?
A
- same atoms could be arranged in different functional groups
-these isomers have very different physical and chemical properties
21
Q
How are different compounds in crude oil separated?
A
- by fractional distillation
22
Q
What is crude oil?
A
- a mixture of substances
-most of which are hydrocarbons
23
Q
What are hydrocarbons?
A
- molecules which are made of only carbon and hydrogen only
24
Q
What is the method for fractional distillation when crude oil is separated?
A
- oil is heated until most of it has turned into gas
-gases enter a fractionating column
-in the column there is a temp gradient (when substances that make up the crude oil reach a part of the column where the temp is lower than their boiling point, they condense)
-bubble caps in fractionating column stop separated liquids from running back down the column and remixing
-you end up with he crude oil mixture separated into different fractions
-each fraction contains a mixture of hydrocarbons with similar boiling points - and also saturated and unsaturated hydrocarbons
25
What do saturated hydrocarbons contain?
- single bonds between carbon atoms
26
What do unsaturated hydrocarbons contain?
- double or triple bonds between carbon atoms
27
What are refinery gases?
- 3 carbons
- used in domestic heating and cooking
28
What is Gasoline?
- 8 carbons
- used as a fuel in cars
29
What is Kerosene?
- 15 carbons
- used as a fuel in aircraft
30
What is Diesel?
- 20 carbons
- used as a fuel in some cars and larger vehicles (trains)
31
What is Fuel Oil?
- 40 carbons
- used as a fuel for large ships and also in some power stations
32
What is Bitumen?
- 70+ carbons
- used to surface roads and roofs
33
What do long hydrocarbons have?
- high boiling points
- viscous (thick and gloopy)
34
What do shorter hydrocarbons have?
- lower boiling points
- much thinner and paler in colour
35
What is the demand for hydrocarbons?
- short chain hydrocarbons like octane (used in petrol) is much higher demand than long-chain hydrocarbons
36
How do you meet the demand for hydrocarbons?
- long chains of hydrocarbons are split into more useful short-chain molecules using cracking
37
What is cracking?
- form of thermal decomposition, which just means breaking molecules down into simple molecules by heating them
38
What does cracking also produce?
- produces alkenes
- used to make polymers
39
What are vaporised hydrocarbons passed over?
- a powdered catalyst at about 600 degrees- 700 degrees
- Silica or alumina are used as the catalyst
40
What can you use for cracking?
- vaporised alkane
- a mixture of shorter chain alkanes and alkenes
- catalyst
41
What happens during the cracking experiment?
- alkane is heated until it is vaporised
- it then breaks down when it comes into contact with a catalyst
- producing a mixture of short chain alkanes and alkenes
42
What happens when you burn a fuel?
- it releases energy in the form of heat
43
What is burning also know as?
- a combustion reaction
- (substance being burned reacts with oxygen)
44
Why do hydrocarbons make great fuels?
- because the combustion reactions that can happen when you burn them in oxygen give out lots of energy
- reactions are exothermic
45
What happens when you burn hydrocarbons in plenty of oxygen?
- products are carbon dioxide and water
- this is called complete combustion
46
What is the equation for complete combustion?
hydrocarbon + oxygen = carbon dioxide + water
47
When do you get incomplete combustion?
- when there is not enough oxygen around for complete combustion
48
What do the products of complete combustion contain?
- less oxygen then carbon dioxide
49
What does incomplete combustion produce?
- carbon monoxide
- a toxic gas and carbon in the form of soot
50
What can carbon monoxide combine with?
- with red blood cells and stop your blood from doing its job of carrying oxygen around the body
- lack of oxygen in the blood supply to the brain can lead to fainting, a coma or death
51
What are a lot of the fractions obtained from crude oil burnt as?
- fuels
52
What happens when the fuels are burnt in the reaction with crude oil?
- sulfur dioxide and nitrogen oxides may be produced
- sulfur dioxide comes with sulfur impurities in the hydrocarbon fuels
53
When are nitrogen oxides created?
- when the temp is high enough for the nitrogen and the oxygen in the air to react
54
What do nitrogen oxides include?
- nitrogen monoxide
- nitrogen dioxide
55
What happens when sulfur dioxide and nitrogen oxides mix with water vapour in clouds?
- they form dilute sulfuric acid and nitric acid
- rain that falls from these clouds is called acid rain
56
What does acid rain cause?
- lakes to become acidic, many plants and animals can die
57
What are alkanes?
- hydrocarbons
- chains of carbon atoms surrounded by hydrogen atoms
58
What do alkanes make up?
- majority of hydrocarbons in crude oil
- tend to combust completely in a good supply of oxygen
59
What is an example of alkanes burning in a combustion reactions? (propane)
propane + oxygen = carbon dioxide + water
60
What do chlorine and bromine react with alkanes in the presence of?
- ultra violet light
61
What is a substitutional reaction?
- hydrogen atom from the alkane is substituted with chlorine or bromine
- this is how bromine and methane react together to form bromomethane
62
What are alkenes?
- hydrocarbons which have a double bond between two of the carbon atoms in their chain
63
Why are alkenes unsaturated molecules?
- they cant make more bonds
- double bond can open up, allowing the two carbon atoms to bond with other atoms
64
What are the first three alkenes?
- ethene
- propene
- butene
65
What do Halogens react with alkenes to form?
- Haloalkenes
66
Why is Dibromoethane an additional reaction?
- the C=C double bond is split and a halogen atom is added to each of the carbons
67
What is the reaction between bromine and alkenes often used as a test for?
- carbon-carbon double bonds
68
What happens when you shake an alkene with orange bromine water?
- the solution becomes colourless
-this is because the bromine molecules which are orange are reacting with the alkene to make dibromoalkane which is colourless
69
Why dont alkanes react with bromine water?
- they dont have a double bond
70
What would happen if you add an alkane to bromine water?
- the solution will stay orange
