AS chemistry unit 2

HideShow resource information
  • Created by: Elena
  • Created on: 26-05-14 17:30
What does Molecular shape depend on?
The number of electron pairs around the central atom, in the outer shell
1 of 228
Which repels more? Bonding pairs or lone pairs?
Lone pairs so the greatest angles are between lone pairs of electrons and bonding pairs are often pushed closer together by lone-pair repulsion
2 of 228
Which angles are the biggest?
Lone-pair/lone-pair bond angles are the biggest
3 of 228
Which angles are the smallest?
Bonding-pair/bonding pair bond angles are the smallest
4 of 228
What is the electron-pair repulsion theory?
The shape of a molecule or ion is determined by the arrangement of electron pairs around the central atom
5 of 228
What kind of atoms have their bonds arranged like a tetrahedron?
Single-bonded carbon atoms as carbon makes four single bonds and so the angle between any 2 of the covalent bonds is 109.5 - the bonds are as far apart from each other as possible.
6 of 228
What shape are molecules that have 2 electron pairs on a central atom?
Linear - bond angle is 180. Examples: BeCl2 & CO2
7 of 228
What shape are molecules that have 3 electron pairs on a central atom and no lone pairs
Trigonal planar - bond angle is 120. Examples: BCl3 & CO3^2-
8 of 228
What shape are molecules that have 3 electron pairs on a central atom and 1 lone pair?
Non-linear or bent - 120. Examples: NO3- & SO2
9 of 228
What shape are molecules that have 4 electron pairs on a central atom and no lone pairs?
Tetrahedral - Bond angle is 109.5 and examples are: NH4+
10 of 228
What shape are molecules that have 4 electron pairs on a central atom and one lone pair?
Trigonal pyramidal - bond angle is 107 and examples are: NH3 and SO3^2-
11 of 228
What shape are molecules that have 4 electron pairs on a central atom and two lone pairs?
non-linear or bent - bond angle is 104.5 and an example is H2O
12 of 228
What shape are molecules that have 5 electron pairs on a central atom and no lone pairs?
Trigonal bipyramidal - bond angle is 120 and 90 and examples are: PCl5
13 of 228
What shape are molecules that have 6 electron pairs on a central atom and no lone pairs?
Octahedral - bond angle is 90 and examples are SF6
14 of 228
What is the hardest known substance?
15 of 228
What are allotropes?
Different forms of the same element in the same state
16 of 228
How many allotropes does Carbon have? and what are they called?
Carbon has 3 allotropes; Diamond, graphite and fullerenes
17 of 228
What is the difference between the allotropes?
They each have a different giant molecular structure
18 of 228
What are the main features of diamond?
Made up of carbon atoms - each carbon is covalently bonded with sigma bonds to four other carbon atoms = tetrahedral shape (it's crystal lattice structure)
19 of 228
What do the strong covalent bonds in Carbon do?
Make Diamond have a very high melting point (sublimes- straight from solid to gas) - makes diamond very hard - Vibrations travel easily through stiff lattice so it's a good thermal conductor - Can't conduct electricity and won't dissolve in anything
20 of 228
What does macromolecular mean?
a very large molecule, as a colloidal particle, protein, or especially a polymer, composed of hundreds or thousands of atoms.
21 of 228
How are the carbon atoms arranged in graphite?
Arranged in sheets of flat hexagons covalently bonded with 3 bonds each. The fourth outer electron of each carbon atom is delocalised
22 of 228
What makes graphite slippery and great for using as a dry lubricant and in pencils?
It has weak bonds between layers are easily broken so sheets can slide over each other
23 of 228
What causes an electric current to be able to flow through graphite?
The 'delocalised' electrons in graphite aren't attached to any particular Carbon atoms and are free to move along the sheets
24 of 228
Why is graphite used to make strong, lightweight sports equipment?
The layers are quite far apart compared to the length of the covalent bonds, so graphite is less dense that diamond
25 of 228
What property of graphite is caused by the strong covalent bonds?
Graphite has a very high melting point - it sublimes at over 3900K
26 of 228
What 2 properties do graphite and diamond have in common?
Both have high melting points due to the strong covalent bonds and both can't dissolve in any solvent due to strong covalent bonds which are too difficult to break
27 of 228
What is the shape of a fullerene?
Fullerenes are molecules of carbon shaped like hollow balls or tubes
28 of 228
How many bonds to each carbon atom form in fullerenes and what property does this give them?
Each carbon atom forms 3 covalent bonds with it's neighbours, leaving free electrons that can conduct electricity
29 of 228
What was the first fullerene to be discovered?
Buckminsterfullerene - 60 carbon atoms joined to make a ball - C60 - occurs naturally in soot
30 of 228
Are fullerenes soluble or non-soluble?
Soluble in organic solvents and form brightly coloured solutions
31 of 228
Due to the fact fullerenes are hollow, what are they used to do?
'cage' other molecules. Fullerene structure forms around another molecule, which is then trapped inside - used as a way of delivering a drug into specific cells of the body
32 of 228
What type of technology are fullerenes used in?
They are used in nanotechnology - materials and devices made from nanoparticles and at this tiny scale, materials often have very different properties from 'bulk' forms of the same substance
33 of 228
Which is a carbon nanotube?
It's like a single layer of graphite rolled up into tiny hollow cylinders
34 of 228
What are the properties of nanotubes?
All covalent bonds makes them very strong & used to reinforce graphite to make them stronger. Conduct electricity so can be used as tiny wires in circuits for computer chips. Ends of nanotubes can be capped to create large molecular cage structure
35 of 228
What have scientists found out about nanoparticles?
They seem to be able to pass through the skin and into cells. If they can do that, then there's a possibility that they could damage the cells
36 of 228
What is electronegativity?
The ability to attract the bonding electrons in a covalent bond
37 of 228
How is electronegativity measured?
Using The Pauling scale
38 of 228
What is the most electronegative element?
Fluorine is the most with a value of 4.0 on the Pauling scale and oxygen, nitrogen and chlorine are also very strongly electronegative
39 of 228
Why are covalent bonds polarised?
By differences in electronegativity
40 of 228
In a covalent bond between 2 atoms of different electronegativities , where are the bonding electrons pulled to?
The bonding electrons are pulled towards the more electronegative atom - makes bond polar
41 of 228
What are the covalent bonds in diatomic gases such as hydrogen and chlorine?
They are non-polar because the atoms have equal electronegativities and so the electrons are equally attracted to both nuclei.
42 of 228
In a polar bond, what does the difference in electronegativity between the 2 atoms cause?
A dipole - a difference in charge between the 2 atoms caused by a shift in electron density in the bond.
43 of 228
The greater the difference in electronegativity...
The more polar the bond
44 of 228
Whether a molecules itself is polar depends on what?
It's shape and the polarity of its bonds
45 of 228
In covalent bonds, there is an attraction between the nuclei and the shared electrons but what repels each other?
The 2 positively charged nuceli repel each other, as do the electrons so the distance between the 2 nuclei is the distance where the attractive and repulsive forces balance out - bond length.
46 of 228
The stronger the attraction between the atoms...
The higher the bond enthalpy and the shorter the bond length.
47 of 228
What kind of forces are very weak?
Intermolecular forces - much weaker than covalent, ionic or metallic bonds
48 of 228
How many types of intermolecular forces are there and what are they called?
There are 3 types: instantaneous dipole-induced dipole (London forces) = weakest type. Permanent dipole-permanent dipole interactions and hydrogen bonding (strongest type)
49 of 228
What type of intermolecular force is found between all atoms and molecukes?
London forces - cause all atoms and molecules to be attracted to each other
50 of 228
What causes a temporary dipole?
At 1 moment, electrons in atom are likely to be more to one side that the other = atom would have a temporary dipole which causes another temporary dipole in the opposite direction of neighbouring atom - 2 dipoles attracted to each other
51 of 228
What do stronger london forces mean?
Higher melting and boiling points
52 of 228
What does the boiling point of alkanes depend on?
It's shape and size
53 of 228
Smallest alkanes are gases at room temperature which means they have...?
Very low boiling points
54 of 228
Larger alkanes are liquid at room temperature which means they have...?
Higher boiling points
55 of 228
Why do straight-chain alkanes have higher boiling points that branched alkanes?
Branched-chain alkanes have smaller molecular surface areas and they can't pack as closely together - London forces are reduced.
56 of 228
Why do long-chain alkanes have higher boiling points than short-chain alkanes?
The longer the carbon chain, the stronger the london forces - there's more molecular surface area and more electrons to interact.
57 of 228
What type of molecules have Permanent Dipole-Dipole forces?
Polar molecules - s- & s+ charges on polar molecules cause weak electrostatic forces of attraction between molecules.
58 of 228
What is the strongest intermolecular force?
Hydrogen bonding
59 of 228
When does hydrogen bonding happen?
When hydrogen is covalently bonded to fluorine, nitrogen or oxygen (very electronegative so they draw bonding electrons away from hydrogen atom)
60 of 228
Molecules that have hydrogen bonding are usually?
Organic, containing -OH or -NH groups. Water and ammonia both have hydrogen bonding
61 of 228
How does hydrogen bonding have an affect on the properties of substances?
Have higher melting and boiling points than similar molecules due to extra energy needed to break H bond so water and HF have a much a higher boiling point than other hydrogen halides.
62 of 228
What is solubility affected by?
Bonding - bonds in solvent and substance have to break and new bonds have to form between solvent and substance
63 of 228
Usually a substance will only dissolve when?
If the strength of the new bonds formed is about the same as, or greater than, the strength of the bonds that are broken
64 of 228
What are the 2 main types of solvents?
Polar solvents (water) which bonds to each other with hydrogen bonds and non-polar solvents (hexane) which bond to each other by London forces.
65 of 228
What do ionic substances dissolve in?
Polar solvents such as water - ions attracted to oppositely charged ends of water molecules. Ions pulled away from ionic lattice by H2O molecules (surround ions) - hydration. Some ionic substances don't dissolve cause bonds are too strong
66 of 228
What is hyrdration?
When the ion are pulled away from the ionic lattice by the water molecules, which surround the ions
67 of 228
What do alcohols dissolve in?
Polar solvents such as water - polar O-H bonds in alcohol attracted to polar O-H bonds in H2O. H bonds form between lone pairs on the s- O atoms and the s+ H atoms
68 of 228
What makes alcohols more soluble or less soluble in polar solvents?
The carbon chain part of alcohol isn't attracted to water, so the more carbon atoms there are, the less soluble the alcohol will be - only the O-H bond is attracted to the water
69 of 228
Why do not all molecules with polar bonds dissolve in water?
Such as halogenalkanes - they contain polar bonds but their dipoles aren't strong enough to form H bonds with water. H bonds between H2O molecules is stronger than bonds that would be formed with halogenalkanes so they don't dissolve.
70 of 228
What does 'like dissolves like' mean?
Substances usually dissolve best in solvents that have similar bonds.
71 of 228
What is a redox reaction?
When electrons are transferred
72 of 228
What is the loss of electrons called?
73 of 228
What is the gain of electrons called?
74 of 228
What does an oxidising agent do?
Accepts electrons and gets reduced
75 of 228
What does a reducing agent do?
Donates electrons and gets oxidised
76 of 228
What oxidation number do uncombined elements and elements bonded to identical atoms have?
77 of 228
What is the oxidation number of a simple monatomic ion?
The same as it's charge so Na+ would be +1
78 of 228
When do oxidation numbers go up or down?
When electrons are lost or gained. Increase if electrons are lost and decrease if electrons are gained.
79 of 228
What does disproportionation mean?
When as element is both oxidised and reduced at the same time
80 of 228
What do ionic half-equations show?
Oxidation or reduction
81 of 228
Does ionisation energy increase or decrease down the group?
Decreases - each element going down has an extra electron shell and so the inner shells shield the outer electrons from the nucleus' attraction. Extra shell means electrons are further away from nucleus - makes it easier to remove outer electron
82 of 228
What do group 2 elements react with?
Water, oxygen and chlorine. Group 2 elements are oxidised from a state of 0 to +2 because they contain 2 electrons on their outer shell
83 of 228
Group 2 element + water -->
Metal hydroxide + hydrogen. They get increasingly reactive down the group because ionisation energy decreases
84 of 228
Group 2 element burns in oxygen -->
Forms a solid white oxide but has characteristic flame colours
85 of 228
Group 2 element + chlorine -->
Forms a solid white cholride
86 of 228
What do solubility trends depend on?
The compound anion
87 of 228
What increases in solubility down group 2?
Group 2 elements that contain singly charged negative ions (OH-)
88 of 228
What decreases in solubility down group 2?
Compounds that contain doubly charged negative ions (SO4^2- and CO3^2-)
89 of 228
Solubity if hydroxides?
increase down the group
90 of 228
Solubility of sulfates?
Decrease down the group
91 of 228
Which sulfate is insoluble in water?
Barium sulfate as it is one of the lowest group 2 element
92 of 228
What is thermal decomposition?
When a substance breaks down (decomposes) when heated. The more thermally stable a substance is, the more heat it will take to break it down.
93 of 228
Does thermal stability of carbonates and nitrates increase or decrease down group 1 and 2?
Increases down the group - carbonate and nitrate ions are large & can be made unstable by presence of +ve charged ion (cation) which polarises anion, distorting it. Greater distortion = less stable the anion.
94 of 228
Going further down the group means the cation gets larger which means...
Large cations cause less polarisation than small cations and size increases down the group so the further down the group, the less distortion caused and the more stable the carbonate/nitrate anion.
95 of 228
Are group 1 or group 2 compounds more thermally stable?
Group 1 compounds are more thermally stable than group 2 compounds - the greater the charge on the cation, the greater the distortion and the less stable the carbonate/nitrate ion is. Group 2 cations have 2+ charge compared to Group 1's +1 charge.
96 of 228
What do group 2 carbonates decompose to form?
They form the oxide and carbon dioxide
97 of 228
What do group 1 nitrates decompose to form?
The nitrate and oxygen
98 of 228
What do group 2 nitrates decompose to form?
The oxide, nitrogen dioxide and oxygen
99 of 228
What do group 1 carbonates decompose to form?
They are thermally stable and so you can't heat them enough with a bunsen to make them decompose (do decompose at higher temperatures)
100 of 228
How to test how easily nitrates decompose
How long it takes till oxygen is produced (relight glowing splint) or how long it takes till brown gas (NO2) is produced - NO2 is toxic so has to be done in fume cupboard
101 of 228
How to test how easily carbonates decompose
How long it takes for CO2 to be produced - using lime water which turns cloudy with CO2.
102 of 228
What colour is Lithium when it burns?
103 of 228
What colour is sodium when it burns?
104 of 228
What colour is potassium when it burns?
105 of 228
What colour is rubidium when it burns?
106 of 228
What colour is caesium when it burns?
107 of 228
What colour is the flame of Calcium when it burns?
108 of 228
What colour is the flame of Strontium when it burns?
109 of 228
What colour is the flame of Barium when it burns?
110 of 228
What colour is the flame of Magnesium when it burns?
111 of 228
How does a flame test work?
Mix small amount of compound you're testing with HCl & heat platinum/nichrome wire in hot bunsen flame (cleans it). Dip wire into compound/acid mixture and note colour produced
112 of 228
What is electron transition?
The movement of electrons between energy levels
113 of 228
What is the explanation of a flame test?
Energy absorbed from flame - electrons move to higher energy levels - colours are seen as electrons fall back down to lower energy levels, release energy in form of light.
114 of 228
What determines the colour of the flame?
The difference in the energy between the higher and the lower levels determines the wavelength of the light released which determines the colour of the light
115 of 228
What are the halogens?
The highly reactive non-metals of Group 7
116 of 228
What colour is the solution of bromine + water?
117 of 228
What colour is the solution of iodine + water?
118 of 228
What colour is the solution of iodine + hexane?
119 of 228
What colour is the solution of bromine + hexane?
120 of 228
What happens to halogen's reactivity down the group?
It decreases down the group
121 of 228
Are halogens oxidising or reducing agents?
They're oxidising agents so they're reduced
122 of 228
Whey are larger atoms (going down the group) less reactive?
Outer electrons are further from nucleus and there is more shielding - harder for larger atoms to attract the electron needed to form an ion - become less oxidising
123 of 228
Does mp and dp increase or decrease down the halogens?
Increases down the group
124 of 228
Why has Astatine not been studied yet?
Because it's highly radioactive and decays quickly
125 of 228
What undergos disproportionation with halogens?
Alkalis - hot and cold solutions.Halogen is both oxidised and reduced at the same time
126 of 228
What do halogens oxidise?
Metals, non-metals and some ions
127 of 228
What is an example of a halogen oxidising a metal?
Fluorine and Chlorine react with hot iron to form iron(III) halides and Bromine (weaker oxidising agent) gets a mixture of iron(II) and iron(III) bromide. With iodine - only iron(II) iodide forms
128 of 228
What is an example of a halogen oxidising a non-metal?
Chlorine reacts with sulfur to form sulfur(I) chloride
129 of 228
What is an example of a halogen oxidising an ion?
All halogens except iodine will oxidise iron(II) ions to iron(III) ions in solution - change colour from green to orange
130 of 228
The reducing power or halides increases or decreases down the group?
Increases down the group
131 of 228
What's the difference between a halogen and a halide?
A halogen is the highly reactive non-metals of group 7 (X) or (X2)and a halide is the negative ion (X-)
132 of 228
As you go down the group, the attraction between the halide's nucleus and the outer electrons gets weaker because?
The ions get bigger, so electrons are further away from the positive nucleus and there are extra inner electron shells, so there's a greater shielding effect
133 of 228
Halide + conc sulfuric acid gives?
A hydrogen halide but what happens next depends on which halide you've got
134 of 228
KF or KCl with conc sulfuric (H2SO4) acid?
HF or HCl gas is formed (misty fumes) but HF and HCl aren't strong enough reducing agents to reduce sulfuric acid, so the reaction stops - not a redox reaction.
135 of 228
KBr with Conc sulfuric acid (H2SO4) ?
First reaction gives misty HBr fumes but HBr is a stronger reducing agent that HCl and reacts with H2SO4 in a redox reaction - produces chocking fumes of SO2 and orange fumes of Br2
136 of 228
KI with conc sulfuric acid (H2SO4)?
Gives HI gas in first reaction. HI reduces H2SO4 (same as HBr) but keeps going and reduces SO2 to H2S (toxic gas)
137 of 228
What colour gas are hydrogen halides?
138 of 228
Are hydrogen halide (gas) soluble or non-soluble?
Very soluble, dissolving water to make strong acids - turn blue litmus paper red
139 of 228
Hydrogen halides react with ammmonia gas to produce?
White fumes e.g hydrogen chloride gives ammonium chloride
140 of 228
Halide ions are displaced from solution by?
More reactive halogens. E.g if you mix bromine water, Br2, with potassium iodide solution, the bromine displaces the iodide ions (oxidises them), giving iodine, I2 and potassium bromide, KBr
141 of 228
When will a halogen displace a halide from solution?
If the halide is below it in the periodic table - chlorine displaces bromide and iodide
142 of 228
What forms when a halide reacts with silver nitrate solution?
A coloured precipitate. 1.Add dilute nitric acid to remove ions that may interfere with test, then add silver nitrate solution (AgNO3) --> a precipitate (silver halide)
143 of 228
Silver nitrate test for chloride Cl-
White precipitate, dissolves in dilute NH3
144 of 228
Silver nitrate test for Fluoride F-
No precipitate
145 of 228
Silver nitrate test for Bromide Br-
Cream precipitate, dissolves in conc NH3
146 of 228
Silver nitrate test for iodide I-
Yellow precipitate, insoluble in conc NH3
147 of 228
How do silver halides react with sunlight?
Silver halides decompose when light shines on them, producing silver and the halogen
148 of 228
Put these in the order of most strongly reducing to least strongly reducing: Cl-, I-, Br- and F-
I-, Br-, Cl- and F-
149 of 228
What is a pipette used for in a titration?
It measures only one volume of solution - Pipette is filled to just above the line and then pipette is taken out of the solution and the level is then dropped carefully to the line
150 of 228
What is a burette used for in a titration?
It measures different volumes and lets you add the solution drop by drop
151 of 228
What are titrations used for?
To calculate the concentration of acid or alkalis solutions - allow you to find out exactly how much acid is needed to neutralise a quantity of alkali
152 of 228
What solution is put into the flask?
The alkali is measured in the burette and put into the flask, along with some indicator such as phenolphalein
153 of 228
What is the end point?
The point where the alkali is exactly neutralised and the indicator changes colour
154 of 228
How do you add the acid to the alkali?
The acid is in the burette and you add it slowly to the flask with the alkali in it and you give the flask a swirl regularly
155 of 228
Why is it best to repeat a titration several times?
To ensure you have the correct end point, makes sure you get the same answer each time, making the results reliable
156 of 228
What do indicators show?
When the reaction's just finished - they change colour. e.g methyl colour turns yellow to red when adding acid to alkali and phenolphthalein turns red to colourless when adding acid to alkali
157 of 228
What is the meaning of uncertainty?
The amount of error your measurements might have
158 of 228
What pieces of equipment may cause uncertainty in an acid-base titration?
burette - marks every 0.1cm^3, scales - don't give exact mass, measured to the nearest 0.01g. Pipettes and volumetric flasks
159 of 228
Whats the equation to work out percentage uncertainty/error?
Uncertainty/reading x 100
160 of 228
How to minimise some uncertainties?
Buy more precise equipment, calculate percentage error,measure bigger quantities to get smaller percentage error value
161 of 228
What are systematic errors?
The same every time you repeat the experiment - may be caused by the set-up or equipment you're using
162 of 228
What are random errors?
They're what makes the results a bit different each time you repeat an experiment - errors you make when reading from a burette - repeating experiments helps get rid of random errors
163 of 228
What type of errors does repeating the experiment get rid of?
Random errors but not systematic
164 of 228
How do you find the total uncertainty?
Find the percentage error for each bit of equipment, add percentages together = percentage uncertainty in final result & then use this to work out the actual total uncertainty in final result.
165 of 228
What are iodine-sodium thiosulfate titrations used for?
They are a way of finding the concentration of an oxidising agent - the more conc an oxidising agent is, the more ions will be oxidised by a certain volume of it
166 of 228
What goes in the burette in the iodine-sodium thiosulfate titration?
Sodium thiosulfate goes in the burette
167 of 228
Evaluate the titration procedure
contaminated apparatus-make results inaccurate so burette must be clean, and rinsed with sodium thiosulfate. Important to read burette carefully (bottom of meniscus). Experiment should be repeated and average taken. Flask should be washed between exp
168 of 228
What must particles do in order for them to react?
They must collide in the right direction -facing each other the right way. They must also collide with at least a certain minimum amount of kinetic energy = collision theory
169 of 228
What is the activation energy?
The minimum amount of kinetic energy particles need to react
170 of 228
Why does increasing the temperature make a reaction faster?
Molecules will on average have more kinetic energy and will move faster - a greater proportion of molecules will have energies greater than the activation energy and be able to react- curve moves over to right.
171 of 228
What affects the reaction rate?
Temperature, concentration (or pressure), surface area and catalysts
172 of 228
How does increasing the concentration speed up a reaction?
The particles will get closer together on average and if they're closer, they'll collide more which means there is more chance to react
173 of 228
How does increasing the surface area speed up a reaction?
More of the particle can come in contact with other reactants
174 of 228
How can catalysts speed up a reaction?
They lower the activation energy by providing an alternative way for the bonds to be broken and remade. If activation energy is lower, more particles will have enough energy to react
175 of 228
What do catalysts do?
A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy. The catalysyt is chemically unchanged at the end of the reaction
176 of 228
What is a homogeneous catalyst?
It's in the same state as the reactants , so if the reactants are gases, the catalyst must be a gas too.
177 of 228
How does a homogeneous catalyst work?
Forms one or more intermediate compounds with the reactants - products then formed from intermediate compounds = lowers activation energy
178 of 228
How to monitor the reaction rate if a reaction produces a gas?
You can use a gas syringe to record the volume of gas evolved every 10 seconds or so. You could also stand reactant vessel on a balance and the mass will decrease as gas is evolved
179 of 228
How to monitor the reaction rate if a reaction produces a precipitate that clouds a solution?
You can monitor this type of reaction by measuring how quickly a marker becomes invisible through the cloudiness results are subjective - people may not agree when marker disappeared.
180 of 228
Does a dynamic equilibrium happen in an open or a closed system?
In a closed system as nothing can get in or out
181 of 228
What is dynamic equilibrium?
When the forward reaction happens at the same time as the backward reaction
182 of 228
What factors alter the position of equilibria?
Concentration, pressure or temperature so you'll end up with different amounts of reactants and products at equilibrium
183 of 228
If the position of equilibrium moves to the left, you'll get more?
184 of 228
If the position of equlibrium moves to the right, you'll get more?
185 of 228
Do catalysts affect the position of equilibrium?
No, they have no effect; they can't increase yield but they do mean that equlibrium is reached faster.
186 of 228
What experiment can show the effect on equilibrium if the concentration is changed?
Iodine(I) chloride in apparatus and pass chlorine gas over it, iodine(III) chloride forms. If pump more chlorine in tube, equilibrium moves right
187 of 228
What experiment can show the effect on equilibrium if the temperature is changed?
188 of 228
What experiment can show the effect on equilibrium if the pressure is changed?
189 of 228
Why is predicting the effect of changing conditions really important for industries that use reversible reactions?
They want to make lots of money so they want a way to make as much of useful product as they can and as cheaply as they can. So they need to pick the best conditions for their processes
190 of 228
What is the alcohol homologous series general formula?
191 of 228
What has an impact on whether the alcohol is primary, secondary or tertiary?
Which carbon atom hydroxyl group -OH is bonded to - if it's bonded to a carbon that is attached to one other carbon, it's a primary alcohol and if it's bonded to a carbon that is attached to 3 other carbons, then it's a tertiary alcohol
192 of 228
Which one is more reactive: Primary, secondary or tertiary alcohols?
Tertiary alcohols are more reactive because tertiary alcohols produce the most stable carbocation
193 of 228
What is the best alcohol to start with when making halogenoalkanes? P, S or T
Tertiary alcohols are best to start with when making halogenoalkanes as they are the most reactive - To make chloroalkane, you can just shake a tertiary alcohol with hydrochloric acid - gives an impure chloroalkane
194 of 228
Why can primary and secondary alcohols not be mixed with hydrochloric acid etc?
They react too slowly and so, you need to use phosphorous(III) halide
195 of 228
Why are bromoalkanes and iodoalkanes trickier to make than chloroalkane?
HBr and HI aren't always available 'off the shelf'. Some places suggest using conc H2SO4 and a metal halide (KBr or KI) to produce HBr or HI.
196 of 228
How do you make halogenoalkanes using phosphorous(III) halides?
3ROH + PX3 --> 3RX + H3PO3 = general formula
197 of 228
How do you make chloroalkanes by using phosphorous(V) chloride?
ROH + PCl5 --> RCl + HCl + POCl3 - can be used to test for alcohols, if alcohol is present, steamy fumes of HCl gas are released which turns damp blue litmus paper red.
198 of 228
Alcohols react with what to produce alkoxides?
It reacts with Sodium - sodium metal reacts gently with ethanol, breaking the O-H bonds to produce ionic sodium ethoxide and hydrogen. The longer the hydrocarbon chain of the alcohol gets, the less reactive it is with sodium
199 of 228
What is the equation for sodium metal reacting with sodium to produce alkoxides?
2CH3CH2OH + 2Na --> 2CH3CH2O-Na+ + H2
200 of 228
What part of an alcohol forms hydrogen bonds?
The hydroxyl group -OH.
201 of 228
What properties does the hydroxyl group - OH give to alcohols?
H bonding is strongest intermolecular force - gives alcohols high bp. Alcohol + water forms H bonds - If small alcohol, H bonding lets it mix freely with H2O (miscible)
202 of 228
Why are larger alcohols less miscible in water?
In larger alcohols, most of the molecule is a non-polar carbon chain, so there's less attraction for the polar H2O molecules. This means that as alcohols increase in size, their miscibility in water decreases
203 of 228
Alcohols burn to produce?
Carbon dioxide and water - burns with a pale blue flame. C-C and C-H bonds are broken as ethanol is completely oxidised to make CO2 and H2O = combustion.
204 of 228
What oxidising agent is used to oxidise alcohols?
Acidified potassium dichromate(VI)
205 of 228
What are primary alcohols oxidised to?
Aldehydes and then carboxylic acids. Goes from orange --> green
206 of 228
What are secondary alcohols oxidised to?
Ketones. Goes from orange --> green
207 of 228
What are tertiary alcohols oxidised to?
They won't be oxidised. Stays orange
208 of 228
How do you oxidise a primary alcohol to make an aldehyde?
You gently heat ethanol with potassium dichromate(VI) solution and sulfuric acid in a test tube which should then produce the 'apple' smelling ethanal (aldehyde)
209 of 228
How do you oxidise a primary alcohol to make a carboxylic acid?
Reflux - The alcohol has to be vigorously oxidised and mixed with excess oxidising agent and heated under reflux. This means you can increase the temp of an organic reaction to boiling without losing volatile solvents, reactants or products.
210 of 228
How do you prevent the aldehyde from oxidising further to form the carboxylic acid?
You need to get the aldehyde out of the oxidising solution as soon as it's formed by gently heating excess alcohol with a controlled amount of oxidising agent in distillation apparatus, so the aldehyde is distilled off immediately.
211 of 228
How do you oxidise a secondary alcohol to a ketone?
Refluxing a secondary alcohol (propan-2-ol) with acidified potassium dichromate(VI) will produce a ketone but ketones can't be easily oxidised, so even prolonged refluxing won't produce anything more.
212 of 228
What is the only way to oxidise tertiary alcohols?
By burning them
213 of 228
What tests can be done to distinguish between ketones and aldehydes?
Fehling's or Benedict's solution (blue) turn brick red when warmed with an aldehyde, but not a ketone. Tollen's reagent - reduced to silver when warmed with an aldehyde, but not with a ketone - forms a silver mirror.
214 of 228
What is a primary halogenoalkane?
The halogen is attached to a carbon that is attached to one other carbon atoms (alkyl groups)
215 of 228
What is a secondary halogenoalkane?
The halogen is attached to a carbon that is attached to two other carbon atoms (alkyl groups)
216 of 228
What is a tertiary halogenoalkane?
The halogen is attached to a carbon that is attached to 3 other carbon atoms (alkyl groups)
217 of 228
What experiment could you use to compare the reactivity of primary, secondary and tertiary halogenoalkanes?
Mix halogenoalkane with water to form an alcohol & put silver nitrate solution in mixture too - silver ions react with halide ions giving silver halide precipitate. Tertiary forms immediately, secondary takes several seconds and primary takes minutes
218 of 228
What are halogenoalkanes used for?
Used to produce useful polymers, used in refrigerators, fire retardants or flame retardants.
219 of 228
What are CFCs?
Chlorofluorocarbons - halogenoalkanes in which all the H atoms have been replaced by chlorine and fluorine atoms - cause damage to ozone layer so they were banned.
220 of 228
What halogenoalkanes are now used instead of CFCs?
a mixture of difluoromethane and pentafluoroethane (refrigerant) - doesn't harm ozone layer. Hydrochlorofluorocarbons (HCFCs) are less damaging to ozone because they're less stable and decompose lower in atomosphere.
221 of 228
IS the carbon-halogen bond polar or non-polar and why?
The carbon-halogen bond is polar because halogens are much more electronegative than carbon
222 of 228
What is a nucleophile?
An electron-pair donor which donates an electron pair to somewhere without enough electrons
223 of 228
What can the nucelophile bond to in a halogenoalkane?
It bonds with the slightly +ve carbon because the carbon doesn't have enough electrons and therefore, the nucleophile is substituted for the halogen = nucleophilic substitution.
224 of 228
Halogenoalkanes react with aqueous alkalis to form alcohols how?
You substitute the -OH for the halogen - hydrolysis
225 of 228
How does water act as a nucleophile?
Water is a weak nucleophile but will be substituted for the halogen eventually = alcohol.
226 of 228
How do halogenoalkanes react with ammonia to form amines?
You warm a haloalkane with excess ethanolic ammonia, the ammonia swaps places with the halogen (nucleophilic substitution).
227 of 228
How does a halogenoalkanes undergo elimination reactions?
If you react a halogenoalkane with a warm alkali dissolved in alcohol, you get an alkene - mixture must be heated under reflux or volatile stuff will be lost.
228 of 228

Other cards in this set

Card 2


Lone pairs so the greatest angles are between lone pairs of electrons and bonding pairs are often pushed closer together by lone-pair repulsion


Which repels more? Bonding pairs or lone pairs?

Card 3


Lone-pair/lone-pair bond angles are the biggest


Preview of the back of card 3

Card 4


Bonding-pair/bonding pair bond angles are the smallest


Preview of the back of card 4

Card 5


The shape of a molecule or ion is determined by the arrangement of electron pairs around the central atom


Preview of the back of card 5
View more cards


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all AS unit 2 edexcel resources »