TOPIC 6 Organic Chemistry Flashcards
1
Q
A saturated hydrocarbon molecule contains four carbon atoms. How many hydrogen atoms does it have in a molecule?
A
10
2
Q
Consider the compound with the formula C2F4
(a) Is it an organic compound? Explain your answer
(b) Is it saturated or unsaturated? Explain your answer
A
(a) yes because it contains carbon atoms
(b) unsaturated as it contains a C=C double bond
3
Q
What is structural isomerism?
A
Same molecular formula, different structural formula
4
Q
What is chain isomerism?
A
A type of structural isomerism when molecules have different carbon chains
5
Q
What is position isomerism?
A
A type of structural isomerism when the same functional group is attached in different positions on the same carbon chain
6
Q
What is stereoisomerism?
A
Same molecular formula, same structural formula but different arrangement
7
Q
What is geometric isomerism?
A
A type of stereoisomerism when the C=C bond fixes the position of the atoms or groups attached at different positions
8
Q
Why does cis-trans notation not work with all compounds?
A
Because there needs to be a double bond for it to occur
9
Q
When naming E-Z isomers, what does priority mean?
A
The atom with the highest atomic number
10
Q
What are the three types of fossil fuel?
A
Coal, crude oil and natural gas
11
Q
Which organic compound are crude oil and natural gas mainly composed of?
A
Alkanes
12
Q
What are the three main ways in which crude oil is converted into fuels?
A
Fractional distillation
Cracking
Reforming
13
Q
How does fractional distillation work?
A
Crude oil is heated in a furnace and then passed into a column where it condenses based on each compounds boiling point
14
Q
What type of compounds condense at the bottom of a fractioning column?
A
Large molecules, with longer chains and higher boiling temperatures
15
Q
What type of compounds condense at the top of a fractioning column?
A
Small molecules, with shorter chains and lower boiling temperatures
16
Q
What does cracking do?
A
Break long chain molecules into shorter chain molecules
17
Q
Why is cracking used?
A
there is a surplus in longer chain molecules and they do not have many uses but there is a high demand for shorter chained molecules as they are better fuels and can be used to make other substances such as polymers
18
Q
How is cracking carried out?
A
The hydrocarbons are passed through a heated catalyst, usually zeolite
19
Q
What is reforming?
A
Converting straight-chains alkanes into branched and cyclic alkanes
20
Q
Why is reforming done?
A
Because straight chain alkanes burn less effectively than branched and cyclic ones
21
Q
How is reforming carried out
A
The straight chain alkanes is heated with a catalyst (usually platinum)
22
Q
One molecule of the alkane C12H26 is cracked to form two molecules of ethene and one molecule of a different alkane. What is the molecular formula of the alkane formed?
A
C8H18
23
Q
The products of a cracking reaction are two molecules of ethene and one molecule of pentane. What is the molecular formula of the alkane cracked?
A
C9H20
24
Q
Why are alkanes burned? Give an example
A
To provide energy such as propane which is sold in containers at higher pressure for used as a fuel in homes and when camping
25
Why does incomplete combustion sometimes occur? (2)
Insufficient oxygen
| Combustion is very rapid
26
When carbon is produced during complete combustion, how is it seen and what other products are formed?
Smoke in the air or spot on the burner
| Carbon dioxide and water
27
Why is carbon monoxide deadly?
It is a toxic gas that prevents the transport of oxygen around the body
28
What else can sometimes occur in incomplete combustion and what happens when this occurs?
The hydrocarbon doesn’t burn at all and a small proportion of the hydrocarbons are released into the atmosphere unchanged ( known as unburned hydrocarbons , HC )
29
What else can be found in crude oil and why are they difficult to remove?
Atoms containing sulphur , cannot be removed by fractional distillation , cracking or reforming
30
What are the chemical reactions that occur with sulphur atoms during combustion? (2)
S + O2 —> SO2
| 2SO2 + O2 —> 2SO3
31
SO2 and SO3 are acidic oxides- what does this mean and what are the chemical reactions?
They dissolve in water in the atmosphere:
SO2 + H2O —> H2SO3 ( sulphurous acid )
SO3 + H2O —> H2SO4 ( sulphuric acid )
32
What do sulphurous acid and sulphuric acid contribute to and what is the effect of this?
Formation of acid rain - responsible for a lot of environmental damage , including damage to aquatic life in lakes and rivers , and damage to crops and forests
33
What are the equations for the combustion of alkanes containing nitrogen, what conditions are needed and what are the properties of some of the products? (3)
All occur at high temperatures
N2 + O2 —> 2NO
2NO + O2 —> 2NO2 —> acidic , can dissolve
2NO2 + H2O —> HNO2 + HNO3 —> both contribute to environmental damage
34
What metals do catalytic converters contain (3) and how are they made?
Platinum , palladium and rhodium
| Spread thinly over a honeycomb mesh to increase the surface area
35
Which pollutants do 3-way catalytic converters remove?
Carbon Monoxide , unburned hydrocarbons and oxides of nitrogen
36
What are the 3 chemical reactions that occur in 3-way catalysts?
2CO + O2 —> 2CO2 ( oxidation of CO )
C8H18 + 12.5O2 —> 8CO2 + 9H2O ( oxidation of unburned hydrocarbons )
2NO + 2CO —> N2 + 2CO2
37
Which type of compounds are catalysts which are currently used not very good are getting rid of?
Sulphur compounds
38
What is the best way to prevent sulphur based pollution?
Remove the sulphur compounds before the fuel is burned
39
Summarise information about the products of combustion of alkanes, including names and whether complete or incomplete combustion was involved
Complete combustion: carbon dioxide and water
| Incomplete combustion: carbon , carbon dioxide and water OR carbon monoxide , carbon dioxide and water
40
No carbon dioxide is formed when hydrogen is burned. Suggest why hydrogen is not a carbon neutral fuel.
Hydrogen does not occur naturally, it has to be manufactured. This uses energy, some of which comes from burning fossil fuels.
41
Summarise reasons why biofuel may not be carbon neutral.
The plants from which biofuels are obtained may need fertilising by pesticides produced from organic chemicals. The plants are then harvested, transported and processed using energy from fossil fuels.
42
What are the 3 mains concerns about the combustion of fossil fuels?
Pollution caused by combustion
The depletion of natural resources
Global warming and climate change
43
What is the purpose of biofuels?
Type of new fuel that is an alternative to fossil fuels
44
What are some examples of renewable resources? (5)
```
Biofuels
Sunlight
Wind
Waves and tides
Geothermal energy
```
45
What are some examples of non-renewable resources? (3)
Coal
Oil
Natural gas
46
What is carbon neutrality in the example of wood?
If a tree is cut down and the wood is burned, then carbon dioxide is formed in combustion - if the amount formed is the same as the amount absorbed then the wood is carbon neutral as the amount of carbon dioxide in the atmosphere has not been altered by its combustion
47
Why are fossil fuels, such as those formed from trees, not carbon neutral?
The carbon dioxide was absorbed from the atmosphere millions of years ago when the amount in the atmosphere was much higher. Therefore, when fossil fuels are burned, the amount of carbon dioxide in the atmosphere increases
48
What is biodiesel?
Starting materials - present in vegetable oils such as those obtained from rapeseed and sunflowers
Proving a very effective alternative to ordinary diesel and can also be mixed with ordinary diesel
49
What are bioalcohols?
Most common is bioethanol
Refers to the ethanol produced in a different way involving bacterial rather than enzymes —> also possible to use a much wider range of plants and also plant waste
The upper limit to the amount of ethanol that can be obtained from a given amount of starting material is increasing and is much fighter than fermentation
50
Why are alkanes fairly unreactive?
They contain only carbon and hydrogen atoms and single bonds
The bonds are not very polar and so do not undergo reactions with substances that are considered to be very unreactive , such as acids and alkalis and reactive metals
51
What do mechanisms do?
Try to explain the actual changes that occur during a reaction, especially in the bonding between the atoms.
52
Under what conditions does the chlorination of methane occur?
High temperatures OR
| Room temperature if the mixture is exposed to ultraviolet radiation
53
What is step 1 in the halogenation of an alkane?
Initiation
UV radiation breaks down the chlorine molecule into chlorine atoms
Each chlorine atom takes one electron from the shared pair
This kind of bond breaking is called homolytic fission
54
What is step 2 in the halogenation of an alkane
Propagation
The halogen radical collided with the alkane molecules and they react by removing a hydrogen atom.
The alkyl radical formed then reacts with the halogen molecules
Both equations involve one radical reacting with one radical and produce one radical and one molecule
The 2 steps considered together result in the conversion of an alkane into a halogenoalkane
55
What is step 3 in the reaction of a halogen with an alkane?
Termination reactions
| When 2 radicals collide to form a molecule as the unpaired electrons are shared to form a covalent bond
56
What are further substitution reactions and why do they sometimes occur?
When the hydrogen atoms in the product are replaced one by one with the halogen
It is not easy to prevent them from occurring
57
The general formula for alkenes is CnH2n.
| Why does cyclohexene not have this general formula?
It is a cyclic structure , so it has two fewer hydrogen atoms than the corresponding non-cyclic compound
58
Alkenes are not used as fuels because they are more valuable for other purposes, but they do burn very well. Write an equation for the complete combustion of propene.
C3H6 + 4.5O2 —> 3CO2 + 3H2O
59
What is the general formula of alkanes?
CnH2n+2
60
What is the general formula of alkenes?
CnH2n
61
When drawing structures of alkenes, what angle do you normally show the bond at?
120
62
What is the general formula for cycloalkenes?
CnH2n-2
63
Does the C=C bond makes alkenes more or less reactive?
More reactive
64
What are sigma bonds?
Bonds that occur in all covalent bonds that involve the overlapping of orbitals.
65
What are Pi bonds and when do they occur?
When there are 3 sigma bonds around each carbon atom in ethene, each carbon atom has one electron in a p-orbital that has not been used
The p-orbitals are parallel to each other and are not able to overlap in the same way as sigma bonds
When they do overlap, this results in the formation of two regions of negative charge above and below the sigma bond
This type of bonds is formed by the sideways overlap of orbitals
Each of these regions of negative charge contains one electron so together they make a second pair of electrons between the two carbon atoms
66
Write equations for the reactions between but-2-ene and:
(a) hydrogen
(b) bromine
(c) hydrogen chloride
Using IUPAC rules, write the names of the products of these reactions.
C4H8 + H2 —> C4H10 Butane
C4H8 + Br2 —> C4H8Br2 2,3-dibromobutane
C4H8 + HCl —> C4H9Cl 2-chlorobutane
67
Which is stronger: sigma bond or pi bond? Why?
Sigma bonds because electrons are more tightly held between the 2 carbon atoms than Pi bonds
68
What occurs in most reactions involving alkenes?
A double bond becoming a single bond - the sigma bond remains unchanged but the Pi bond electrons are used to form new bonds with an attacking molecule
69
What is the chemical test for the presence of a C=C bond?
```
Adding bromine ( or bromine water )
Bromine is decolourised (brown/orange —> colourless)
```
70
What is hydrogenation? What are the conditions needed to carry it out?
An addition reaction in which hydrogen is added to an alkene
| Heat + Nickel catalyst
71
How is margarine manufactured?
Naturally occurring vegetable oils are unsaturated but when they react with hydrogen some of the C=C become C-C
This process changes the properties of the vegetable oil and converts it into a solid : margarine
72
What is halogenation? What are it’s products?
An addition reaction in which halogen is added to an alkene
| Produces dihalogenoalkanes
73
What is hydration? What conditions are needed? What does it produce?
An addition reaction in which water ( or H and OH molecules ) are added to an alkene
Hearing the alkene with steam and passing it over a catalyst of phosphoric acid
Produces an alcohol
74
What happens when a alkene is reacted with a hydrogen halide?
An addition reaction which forms a halogenoalkane
75
How is an alkene oxidised to a diol?
An oxidising agent ( potassium manganate (VII) ) is used in acidic conditions ( usually dilute sulphuric acid )
The potassium manganate (VII) provides an oxygen atom and the water in the solution provides another and 2 hydrogen atoms
76
Name the types of reactions that occur when:
(a) alkanes react with halogens
(b) alkenes react with halogens
(a) radical substitution , homolytic fission
| (b) electrophilic addition , heterolytic fission
77
What is the name of the major product formed when but-1-ene reacts with hydrogen chloride?
2-chlorobutane
78
Why does a hydrogen halide react with an alkene?
Alkenes have a Pi bond which means the molecule is electron rich around the C=C bond which makes it attractive to other species that are electron deficient , such a polar molecules like hydrogen halides. These are polar because the halide is more electronegative than the hydrogen.
79
Which end of the hydrogen halide is attracted to the electrons in the Pi bond and why?
The slightly positive end ( hydrogen ) because it has a slightly positive charge
80
What happens in step one of electrophilic addition?
The electrons in the Pi bond move to the positive end of the molecule and the electrons in the bond of the attacking molecule all move to the negative end. 2 ions are formed, one of which is a carbocation.
81
What happens in step 2 of electrophilic addition?
The 2 oppositely charged ions attract each other and react to form a new covalent bond
82
What happens in the electrophilic addition of halogens?
Similar to that of hydrogen halides except the attacking halide doesn’t have a polar bond.
However, as it approached the C=C bond , the electrons in the Pi bond repel the electrons in the bond between the halide atoms and induce the molecule to become polar.
83
What happens in electrophilic substitution when both the alkene and attacking molecule are unsymmetrical?
A major and minor product are formed. Which is which depends of whether the carbocation is primary, secondary or tertiary. Tertiary is the most stable , the secondary followed by primary and so the most stable one will form the major product. This because the positive charge can be spread over more atoms.
84
How are polymers made?
Using compounds with C=C bonds.
Described as addition reactions because the alkene molecules add together in vast numbers
Conditions are a combination of high pressure and high temperature
85
How are polymers named?
‘Poly’ followed by the name of the monomer in brackets. The ending ‘ene’ is still used even though the polymer formed is saturated
86
How are polymers drawn?
The repeat unit is shown in brackets (curved or square)
The letter n is shown as a subscript after the bracket
There are covalent bonds shown passing through the brackets
87
Summarise the advantages of polymers over traditional materials. (3)
Manufactured on a large scale in a variety of shapes and sizes
Lighter in weight
They are unreactive ( don’t corrode or rot )
88
Summarise the advantages (3) and main disadvantage of incineration as a method of disposing of polymer waste.
Very little solid waste
Saves landfill space
Can be used to produce heat energy for homes and factories or to generate electricity
Contains other elements and toxic pollutants which can cause air pollution as they are not very easy to remove
89
What are the main solutions to polymer waste? (2)
Do not use them unnecessarily
| Do not throw away polymer waster
90
What are the 3 ways of putting polymer waste to good uses?
Recycling
Incineration
Chemical feedstock
91
How is the recycling of polymer waste carried out?
Sorting
Processing ( chopping the waste into small pieces and washing it )
Using it to make new materials using methods such as melting, moulding and fibre production
92
How is polymer waste used as a chemical feedstock?
A process , similar to cracking , used to break down the polymer waste into gasses (hydrogen and carbon monoxide)
Produces a feedstock that can be used in other chemical reactions
93
What are the advantages (2) and disadvantages (2) of biodegradable polymers?
Break down unlike traditional plastics
Broken down in the environment
Made from plant material - land is needed
The hydrogen and carbon atoms can not be directly used
94
What are halogenoalkanes?
A homologous series of compounds with the general formula CnH2n+1X
95
What makes halogenoalkanes reactive?
They contain a halogen atom with an electronegativity higher than that of carbon , so the C-X bond is polar
96
What happens to reactivity of halogenoalkanes as you go down group 7 and why does this happen?
They become less reactive as the polarity of the C-X bond decreased as the electronegativity of the halogen decreases
97
What happens in a hydrolysis reaction?
A halogenoalkane is added to water
A water molecule contains polar bonds and so the d- oxygen atom is attracted to the d+ carbon atom
RX + H2O —> ROH + HX
98
How do you compare the rates of hydrolysis reactions?
Add silver nitrate solution so the progress of the reaction can be followed
Use ethanol as a solvent
Control variables such as temperature and the concentration and quantity of halogenoalkanes
Time up to when the precipitate appears
99
Which halogen reacts the fastest in a hydrolysis reaction and why?
Iodine because bond breaking requires energy and the weaker bonds break more easily than stronger bonds and the C-I bond is the weakest
100
Why would you expect chlorine to react the quickest in a hydrolysis reaction and why is this not the case?
Because it is the halogenoalkane with the most polar bond and should be expected to be the fastest to be hydrolysed because the d+ charge on the carbon atom is greatest so the attacking nucleophile should be attracted more strongly , however , there is a more important factor
101
What is the substitution reaction for making alcohols? What is the attacking nucleophile?
Heating a halogenoalkane with aqueous potassium hydroxide under reflux
Attacking nucleophile is the OH- ion
102
What is the substitution reaction for making nitriles? What is the attacking nucleophile?
Heating a halogenoalkane with potassium cyanide dissolved in ethanol under reflux
The attacking nucleophile is the CN- ion
103
What is the substitution reaction for making primary amides? What is the attacking nucleophile?
Heat a halogenoalkane with excess ammonia solution in a sealed tube
The attacking nucleophile is the NH3 molecule
104
Draw and explain the mechanism of the reaction between bromoethane and aqueous potassium hydroxide.
Start with the donation of a lone pair of electrons from the oxygen of a hydroxide ion to the electron deficient carbon atom and the formation of a C-O bond
At the same time , the electrons in the C-Br bond move to the Br atom , resulting in the breaking of the C-Br bond —> heterolytic fission
105
Draw and explain the mechanism for the reaction between chloroethane and ammonia
The first step involves the donation of a lone pair of electrons deficient from the nitrogen of the ammonia to the electron deficient carbon atom and the formation of a C-N bond
At the same time , the electrons in the C-Cl bond move to the Cl atom , resulting in the breaking of the C-Cl bond
The second step involves another ammonia molecule acting as a base and removing a hydrogen ion from the ion formed
106
How are elimination reactions carried out?
Using a different solvent , ethanol instead of water , causes a different reaction to occur
When a halogenoalkane is heated with ethanolic potassium hydroxide , the OH- ion acts as a base and not as a nucleophile
The hydrogen that reacts with the OH- ion is the one attached to a carbon atom next to the C in the C-X bond
107
What is the general formula of alcohols?
CnH2n+1OH
108
What is the equation for the combustion of ethanol?
C2H5OH + 3O2 —> 2CO2 + 3H2O
109
What is halogenation of alcohols?
Replacing the hydroxyl group in an alcohol molecule with a halogen atom
110
How is chlorination of alcohols carried out? What are the inorganic products?
Carried out using phosphorus (V) chloride
The reaction is very vigorous at room temperature
Inorganic products : phosphorus oxychloride and hydrogen chloride
111
How is the chlorination of tertiary alcohols carried out? What is the inorganic product formed?
The alcohol is mixed ( by shaking ) with concentrated HCl at room temperature
H2O is the other product
112
How is the bromination of alcohols carried out? What are the equations? What are the inorganic products formed?
Using a mixture of postassium bromide and about 50% concentration sulphuric acid
The reaction mixture is warmed with alcohol
KBr + H2SO4 —> KHSO4 + HBr
2KBr + H2SO4 —> K2SO4 + 2HBr
Potassium hydrogensulphate
Potassium sulphate
113
What is the equation for the bromination of butan-1-ol?
CH3CH2CH2CH2OH + HBr —> CH3CH2CH2CH2Br + H2O
114
How is the iodination of alcohols carried out? What is the inorganic product formed?
Using a mixture of red phosphorus and iodine
The reaction mixture , including the alcohol , is heated under reflux
The inorganic reagents react first to form phosphorus (III) iodide:
2P + 3I2 —> 2PI3
Inorganic product : phosphonic acid
115
What is the equation for the iodination of ethanol?
3C2H5OH + PI3 —> 3C2H5I + H3PO3
116
How is the dehydration of alcohols to alkenes carried out?
Heating the alcohol with concentrated phosphoric acid
| The OH group and a hydrogen atom from an adjacent carbon atom being removed and a C=C double bond formed in the carbon
117
What is oxidation in terms of alcohols?
The loss of hydrogen from an alcohol molecule
118
Which atoms are removed in the oxidation of alcohols?
The hydrogen of the OH grouoband a hydrogen atom from the carbon atom joined to the OH group
119
Which classification(s) of alcohol can and can’t be oxidised and why?
Primary and secondary alcohols can be but tertiary alcohols can’t be because there isn’t another hydrogen atom attached to the carbon that the OH group is attached to
120
What group does organic product of oxidation contain?
C=O , carbonyl group
121
What are ketones and what is their simplified formula (written and drawn)?
Formed when a secondary alcohol is oxidised
| RCOR
122
What are aldehydes and what is their simplified formula (written and drawn)?
Formed when a primary alcohol is partially oxidised
| RCHO
123
What can sometimes happen when an aldehyde is formed during oxidation, why does this happen and how does it occur?
The aldehyde may be oxidised further to a carboxylic acid as aldehydes are more easily oxidised than alcohols
The process involves the gain of an oxygen atom which goes between the C and H of the CHO group
124
What is a carboxylic acid and what is it’s simplified formula (written and drawn)?
Formed when a primary alcohol is fully oxidised
| RCOOH
125
What is the usual reagent for oxidation reactions and what colour change is seen when this agent is used?
A mixture of potassium dichromate (VI) and dilute sulphuric acid
Orange —> green
126
What is the equation for the oxidation of propan-1-ol to propanal?
CH3CH2CH2OH + [O] —> CH3CH2CHO + H2O
127
What is the equation for the oxidation of propanal to propanoic acid?
CH3CH2CHO + [O] —> CH3CH2COOH
128
What is the equation for the oxidation of propan-2-ol to propanone?
CH3CH(OH)CH3 + [O] —> CH3COCH3 + H2O
129
When the oxidation of an alcohol is intended to be complete , what could be formed and what apparatus would be needed? Include a labelled drawing of this apparatus.
```
Ketone or carboxylic acid
Heating under reflux
Pear shaped flask containing reaction mixture
Condenser vertical
Open top
```
130
When the oxidation of an alcohol is intended to be incomplete , what could be formed and what apparatus would be used? Include a labelled diagram.
Aldehyde
Distillation with addition
Pear shaped flask with oxidising mixture
Alcohol above oxidising mixture in a separating funnel connected by a still head
Horizontal condenser with receiver adaptor at the end with receiver round bottom flask attached collecting the aldehyde
131
Butan-1-ol can be dehydrated to form one organic product but can be oxidised to form 2 organic products. Give the names and structures of these 3 products.
Dehydration:
CH3CH2CHCH2 but-1-ene
Oxidation:
CH3CH2CH2CHO butanal
CH3CH2CH2COOH butanoic acid
132
Pentan-2-ol can be dehydrated to form more than one organic product , but can only be oxidised to form one organic product. Give the names and structures of these products.
Dehydration:
CH3CH2CH2CHCH2 pent-1-ene
CH3CH2CHCHCH3 pent-2-ene
Oxidation:
CH3CH2CH2COCH3 pentan-2-one
133
What might organic products be contaminated by (4)?
Unreacted starting materials
Other organic products
The inorganic reagents used or the inorganic products formed from them
Water
134
Summarise the process of simple distillation and draw a labelled diagram of the apparatus.
Distillation of an impure liquid involves heating it in a flask connected to a condenser
The liquid with the lowest boiling point boils off first and passes into the condenser first so it can be collected separately
135
What is the purpose of a thermometer during distillation?
To monitor the temperature of the vapour as it passes into the condenser.
If the temperature remains steady , this is an indication that one compound is distilling over
If, after a while, the temperature begins to rise, this indicates that a different compound is distilling over
136
What is an advantage of simple distillation over fractional distillation?
It is quicker and easier to set up ; fractional distillation takes a long time to be carried out
137
What is the advantage of using fractional distillation over simple distillation?
Fractional distillation provides better separation and is better for liquids with very similar boiling temperatures
138
Summarise the process of fractional distillation and draw a diagram of the apparatus.
Uses the same apparatus as simple distillation but with a fractioning column between the heated flask and still head
The column is filled with glass beads or pieces of broken glass which acts as surfaces on which the vapour leaving the column can condense and then be evaporated again as more hot vapour passes up the column
Effectively the vapour undergos several repeated distillations as it passes up the column
139
What is solvent extraction?
Using a solvent to remove the desired organic product from the other substances in the reaction mixture
140
What properties does the solvent used in solvent extraction need to have?
Should be immiscible with the solvent
| Must be much less soluble than the desired organic product
141
Summarise the process of solvent extraction and draw a diagram of the apparatus used.
Place the reaction mixture into a separating funnel and then add the solvent - should form a separate layer
Place the stopper in and shake gently
Allow the contents to settle into 2 layers
Remove the stopper and open the tap to allow the lower layer to drain then pour the upper layer into a separate flask
The desired organic product is now mixed with the solvent so should be separated by simple or fractional distillation
142
In solvent extraction , how should the solvent be added and why?
Should be added in small portions because this is more efficient
143
How might water be an impurity in organic products and how is it removed?
Many organic products are prepared using inorganic reagents in aqueous solution
Removed using a drying agent
144
What is an important feature of a drying agent and which are the most common?
Does not react with the organic liquid
Anhydrous metal salts eg. Calcium sulphate, magnesium sulphate and sodium sulphate
All form hydrated salts so when the come into contact with water they absorb it as water if crystallisation
Anhydrous calcium chloride can be used for some organic products although it does react with some and is soluble in alcohols
145
Summarise the process of drying.
The drying agent is added to the organic liquid and the mixture is swirled for shaken and then left for a period of time
Before use, the drying agent is powdery but after absorbing water it looks more crystalline
If a bit more drying agent is added and it stays powdery this is an indication that the liquid is dry
The drying agent is removed either by decantation or filtration
146
How do you test if a liquid is pure?
Measure it’s boiling temperature against that in data booklets - impurities raise the boiling temperature
