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F332 Flashcards

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0
Q

Physical properties of CO2

A

Gas at RT - sublimes from solid
Simple covalent molecule
Many molecules with weak intermolecular bonds, so little energy required to overcome
Carbon able to form double bonds with oxygen due to small size

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1
Q

Physical properties of silicon(iv) oxide

A 
Solid at RT
Very high melting point
Large lattice - one molecule
Strong covalent bonds require a lot of energy to break
Insoluble because of covalent bond
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2
Q

Effect of temperature on reaction rate

A

Doesn’t greatly affect individual molecules’ energy, but does impact proportion of molecules with sufficient energy
Temp rise of 10* doubled rate of reaction
The greater the activation energy, the greater the effect of increasing temp

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3
Q

Effect of pressure on rate of reaction

A

Increases frequency of collisions due to greater number of molecules per unit vol, therefore increasing reaction rate

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4
Q

Effect of concentration on reaction rate

A

Greater number of molecules per unit vol so greater rate

Also affects quantity of product if change is to limiting reagent

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5
Q

Effect of surface area on reaction rate

A

Greater surface area means greater potential for collision, so more frequent collision and reaction rate increases

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6
Q

What is an enthalpy profile?

A

A plot of energy difference between molecules during the progression of a reaction. Highest point shows where old bonds are breaking and new bonds are forming.

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7
Q

What is activation enthalpy?

A

Minimum kinetic energy required by a pair of particles before they will react upon collision.
Energy required to break old bonds so that new bonds can form

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8
Q

Explain the role of catalysts in providing alternative routes of lower activation enthalpy

A

Speeds up a reaction whilst being recovered unchanged at the end
Forms an intermediate, so two steps take place which require a lower energy than the uncatalysed reaction

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9
Q

What is dynamic equilibrium?

A

Takes place in a closed system and is where the rates of forward and backwards reaction are equal, so the concentrations of reactants and products are constant

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10
Q

Impact of change if conc on position of equilibrium

A

Increase of products shifts to reactants

Decrease of reactants shifts to reactants

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11
Q

Impact if change of temperature position of equilibrium

A

Higher temp shifts in favour of endothermic

Cooling shifts to favour exothermic

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12
Q

Impact of pressure on position of equilibrium

A

Increasing shifts to side with fewer gas molecules

Decreasing shifts to side with more gas molecules

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13
Q

Gases present in atmosphere and percentage

A

Nitrogen 78%
Oxygen 21%
Argon 1%
Carbon Dioxide 0.04%

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14
Q

List of pollutants

A 
CO2
CH4
N2O
CO
NOx
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15
Q

Source and impact of CO2

A

Combustion

Greenhouse gas

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16
Q

Source and impact of CH4

A

Cattle, landfill, rice paddy, gas leaks

Greenhouse gas

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17
Q

Source and impact of N2O

A

Fertilised soil

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18
Q

Source and impact of CO

A

Incomplete combustion

Poisonous to humans

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19
Q

Source and impact of NOx

A

Combustion causes air to react

Acid rain, respiratory problems in humans

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20
Q

Bond enthalpy and relation to reactivity of halogens

A

Fluorine has highest bond enthalpy so harder to break, therefore least reactive

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21
Q

Problem with chloroalkanes?

A

Don’t react in troposphere because too stable, so reach stratosphere where the do react, forming radicals which deplete ozone

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22
Q

Homolytic fission

A

Electrons go to different atoms so form two radicals

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23
Q

Heterolytic fission

A

Both electrons go to one atom, so forms ions

Usually occurs when the bond is already polar

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24
Useful properties of CFCs
Non toxic and non flammable Boiling point low enough to evaporate efficiently, freezing point low enough that it doesn't freeze Refrigerants and propellants for aerosols
25
Replacements for CFCs and their advantages/disadvantages
HCFCs have C-H bonds so are broken down in troposphere, so most don't reach the stratosphere, however some do so are not an ideal solution HFCs have no ozone depleting effect even in stratosphere Disadvantage of both is that they are still greenhouse gases
26
How was the hole in the ozone layer discovered?
UV spectroscopy to measure concentrations of ozone Concentrations much lower than expected Replaced instruments to confirm results NASA reexamined old data which had been discounted due to so thought impossible level of inaccuracy, but confirmed results
27
Principle radiation of the earth
Mostly infrared
28
Principle radiation of the sun
IR, vis and UV, but peaking at visible
29
What happens when molecules absorb infrared?
Change in vibrational energy states
30
What happens when molecules absorb uv or vis?
Electrons promoted to higher energy levels
31
Explain the greenhouse effect
Solar energy reaches earth mainly as visible and uv radiation Earth absorbs some of this, heats up, emits IR Greenhouse gases in troposphere absorb some of this IR Increases vibrational energy, transferred to other molecules by collision, increases KE Also reemits IR in all directions, heating earth Increased conc of greenhouse gases enhances this effect
32
What is the evidence for the relationship between the increases conc of greenhouse gases and global warming?
Models which remove human contribution of greenhouse gases predict lower temperate than current global temp These models are shown to be accurate by predicting past climates from given data
33
Different approaches to control of CO2 emissions
Using less fossil fuels Increasing photosynthesis Burying or reacting carbon dioxide to prevent it being released into atmosphere
34
Percentage yield calculation
(mol product/mol reactant) * 100
35
Atom economy calculation
(mr product/mr reactant) * 100
36
Titration for procedure
To calculate conc of acid: Fill and run burette through with acid. Take initial reading. Fill volumetric pipette with alkali, rest meniscus on the mark. Run alkaline solution into conical flask and add 3 drops of indicator. Trial run. Repeat with clean flask, calculating tire, until 3 concordant results are obtained
37
Example electronic configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2
38
How is ozone formed?
``` Oxygen atom (radical) reacts with dioxygen molecule Can also be formed in reactions in photochemical smog in the troposphere ```
39
Effects of ozone in atmosphere
Sunscreen in stratosphere as it absorbs UV that causes sunburn when it photodissociates. This UV can cause skin cancer. Produces photochemical smog in troposphere, caused breathing problems
40
Bond angles
Three pairs - 120 Four pairs - 109 Six pairs - 90, octahedron
41
Physical properties of metallic lattice
High melting point Insoluble Conducts electricity well
42
Physical properties of ionic lattice
High melting point Usually soluble Conducts when molten or dissolved
43
Physical properties of covalent network
Very high melting point Insoluble Don't usually conduct
44
Physical properties of simple covalent molecules
Low melting point Usually insoluble Don't conduct
45
What is electronegativity and what is its trend?
The measure of how strong an atom's pull on an electron is | Tends to peak at period 1 group 7 (fluorine)
46
Dependence of intermolecular bonding on chain length and branching
Chan length increases bonding as greater surface area means higher chance of momentary imbalance Branching reduces bonding because it inhibits proximity of molecules
47
What is oxidation?
Loss of electrons Loss of hydrogen Gain of oxygen
48
What is reduction?
Gain of electrons Gain of hydrogen Loss of oxygen
49
Rules of oxidation state
Atoms in element have 0 Ions add to same as charge on ion In compounds all constituents add to 0
50
Specific oxidation states
F always -1 O always -2 H always +1 except in H- ion Cl always -1 except when combined with O or F
51
Naming inorganic compounds
Roman numeral shows oxidation state of preceding compound (no space between compound and number)
52
What is ionisation enthalpy?
Energy required to remove an electron from each atom in 1 mole of a gaseous sample
53
Trends for ionisation enthalpy
Peaks for noble gases, troughs for group 1 | Higher up table greater than lower down
54
Physical properties of fluorine
Pale yellow gas at RT | Reacts with water
55
Physical properties of chlorine
Green gas at RT | Very low solubility in water
56
Physical properties of bromine
Brown volatile liquid at RT Very high volatility Slightly soluble in water
57
Physical properties of iodine
Shiny black solid at RT Sublimes with warming Very very small solubility in water
58
Advantages of batch
More versatile plant More cost effective in small amounts More applicable to slow reactions
59
Disadvantages of batch
Less control over thermal energy Contamination more likely Larger workforce needed
60
Advantage of continuous
``` More suited to high tonnage production Lower risk of contamination Fine adjustments possible Consistent quality ensured Minimal about and easier automation ```
61
Disadvantage of continuous
Much higher initial cost to build plant | Not cost effective below capacity
62
Reactivity and oxidising ability of halogens
Most reactive at top because smaller and less shielding | Fluorine has highest oxidising ability as it has greatest ability to remove an electron from another atom
63
What happens at electrodes during electrolysis of aqueous halid solution?
Formation of gas eg Cl2 or Br2 at positive | H2 at negative
64
Silver chloride
White
65
Silver bromide
Cream
66
Silver iodide
Yellow
67
Risks of transport and storage of halogens
Fluorine so reactive it would react with any container so has to be produced and used immediately Bromine transported in regulated, lead lined steel tanks
68
Uses of fluorine
PTFE, HCFCs, toothpaste
69
Uses if chlorine
PVC and bleach
70
Uses of bromine
Medicines, flame retardants
71
Uses of iodine
Medicines, human nutrition
72
Describe the preparation of a cholroalkane
Add an alcohol to react with hydrochloric acid Separate the product from the reaction mixture Purify the product Test to confirm its a chloroalkane and test purity
73
Describe and explain the principle stages in the preparation of an organic liquid product
Shake with sodium hydrogen carbonate to remove acidic impurities - weak base to quench acid Separate from other immiscile liquids using separating funnel as they don't mix Dry with anhydrous sodium sulphate to remove water Perform distillation to collect pure product, due to difference in boiling point
74
Characteristic properties of halogenoalkanes
Whilst carbon halogen is polar, not significant enough to make molecule polar or effect properties Boiling point depends on size and number of halogen atoms 2Cl greater than 1I, but 1I greater than 1Br
75
What's hydrolysis?
Breaking of a bond by addition of water
76
What's substitution?
Where one group reacts to replace another group in a molecule
77
What is a nucleophile?
Has a lone pair of electrons it can donate to a positively charged atom to form a covalent bond
78
Reactivity of halogen compounds
C-F bond strongest so least reactive compound C-I weakest so fairly reactive Bond enthalpy shown to override bond polarity
79
What is nitrate(v)?
NO3 -
80
What is sulfate?
SO4 2-
81
What is carbonate?
CO3 2-
82
What is hydroxide?
OH -
83
What is ammonium?
NH4 +
84
What's hydrogen carbonate?
HCO3 -
85
Requirements of hydrogen bonding
Must be large dipole between H and O, N or F H atom is small so can get close to O, N or F in another molecule O, N or F has a lone pair, attracting the positively charged H
86
Solubility of polymers
Polymers with OH groups can form hydrogen bonds When very many, insoluble as water doesn't break their attractions When very few, insoluble polymer doesn't break water attractions
87
What's a carboxylic acid?
R-COOH | Suffix -oic
88
What's an aldehyde?
R-COH | Suffix -al
89
What is a ketone?
R-CO-R' | Suffix -one
90
Difference between primary, secondary and tertiary alcohols?
Primary has one R group Secondary has two R groups Tertiary has three at groups
91
Describe and explain heating under reflux
Reactants in pear-heaped flask and add anti bumping granules Attach condenser vertically to condense escaping vapours and prevent loss of liquids Heat so mixture boils gently
92
What's an elimination reaction?
A small molecule is removed from a larger molecule, leaving an unsaturated molecule In the case of alcohols, this is water Also called dehydration reaction when water is removed
93
What is addition polymerisation?
Where smaller molecules join together to form one large molecule
94
Test for unsaturation
Red-brown bromine water turns colourless
95
Conditions for saturation of alkene
Alkene + Hydrogen Nickel with heat and pressure (150*, 5atm.)(INDUSTRY) Platinum and pressure at room temp (LAB)
96
Conditions for hydration of alkene
Alkene + Water Steam, phosphoric acid, heat and pressure (INDUSTRY) Conc. sulphuric acid and water (LAB)
97
Oxidation of alcohols
Require potassium dichromate(vi) solution Primary to aldehyde then carboxylic acid Secondary to ketone
98
Dehydration of alcohol
Loses water to form an alkene Al2O3 and heat (300*) or H2SO4 and reflux
99
What is an electrophile?
Positive ion or molecule with partial positive charge that will be attracted to a negatively charged region and accept a lone pair of electrons to form a covalent bond
100
How is the mechanism of addition supported experimentally?
Other anions which are present can be incorporated into the molecule
101
Properties of polymers
``` Chain length Side groups Branching Stereo regularity Chain flexibility Cross-linking ```
102
Effect of chain length in polymers
Longer = stronger
103
Effect of side groups in polymers
Polar groups give stronger bonding so stronger polymers
104
Effect of branching in polymers
Unbranched can get closer so bonding is stronger
105
Effect of stereoregularity in polymers
Can pack closer when side groups orientated in a regular way, so stronger
106
Effect of chain flexibility in polymers
More rigid is stronger
107
Effect of cross-linking in polymers
Covalent bonds makes polymer harder and more difficult to melt
108
What is a thermoplastic?
No cross links so can be melted and remoulded
109
What is a thermoset?
Cross linked polymer, so doesn't deform upon heating
110
What's a co-polymer?
Polymer made by addition of more than one kind of monomer

Chemistry (3 decks)

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