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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
Q

Useful properties of CFCs

A

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

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25
Q

Replacements for CFCs and their advantages/disadvantages

A

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

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26
Q

How was the hole in the ozone layer discovered?

A

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

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27
Q

Principle radiation of the earth

A

Mostly infrared

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28
Q

Principle radiation of the sun

A

IR, vis and UV, but peaking at visible

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29
Q

What happens when molecules absorb infrared?

A

Change in vibrational energy states

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30
Q

What happens when molecules absorb uv or vis?

A

Electrons promoted to higher energy levels

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31
Q

Explain the greenhouse effect

A

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

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32
Q

What is the evidence for the relationship between the increases conc of greenhouse gases and global warming?

A

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

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33
Q

Different approaches to control of CO2 emissions

A

Using less fossil fuels
Increasing photosynthesis
Burying or reacting carbon dioxide to prevent it being released into atmosphere

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34
Q

Percentage yield calculation

A

(mol product/mol reactant) * 100

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35
Q

Atom economy calculation

A

(mr product/mr reactant) * 100

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36
Q

Titration for procedure

A

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

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37
Q

Example electronic configuration

A

1s2 2s2 2p6 3s2 3p6 3d10 4s2

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38
Q

How is ozone formed?

A 
Oxygen atom (radical) reacts with dioxygen molecule 
Can also be formed in reactions in photochemical smog in the troposphere
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39
Q

Effects of ozone in atmosphere

A

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

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40
Q

Bond angles

A

Three pairs - 120
Four pairs - 109
Six pairs - 90, octahedron

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41
Q

Physical properties of metallic lattice

A

High melting point
Insoluble
Conducts electricity well

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42
Q

Physical properties of ionic lattice

A

High melting point
Usually soluble
Conducts when molten or dissolved

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43
Q

Physical properties of covalent network

A

Very high melting point
Insoluble
Don’t usually conduct

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44
Q

Physical properties of simple covalent molecules

A

Low melting point
Usually insoluble
Don’t conduct

45
Q

What is electronegativity and what is its trend?

A

The measure of how strong an atom’s pull on an electron is

Tends to peak at period 1 group 7 (fluorine)

46
Q

Dependence of intermolecular bonding on chain length and branching

A

Chan length increases bonding as greater surface area means higher chance of momentary imbalance
Branching reduces bonding because it inhibits proximity of molecules

47
Q

What is oxidation?

A

Loss of electrons
Loss of hydrogen
Gain of oxygen

48
Q

What is reduction?

A

Gain of electrons
Gain of hydrogen
Loss of oxygen

49
Q

Rules of oxidation state

A

Atoms in element have 0
Ions add to same as charge on ion
In compounds all constituents add to 0

50
Q

Specific oxidation states

A

F always -1
O always -2
H always +1 except in H- ion
Cl always -1 except when combined with O or F

51
Q

Naming inorganic compounds

A

Roman numeral shows oxidation state of preceding compound (no space between compound and number)

52
Q

What is ionisation enthalpy?

A

Energy required to remove an electron from each atom in 1 mole of a gaseous sample

53
Q

Trends for ionisation enthalpy

A

Peaks for noble gases, troughs for group 1

Higher up table greater than lower down

54
Q

Physical properties of fluorine

A

Pale yellow gas at RT

Reacts with water

55
Q

Physical properties of chlorine

A

Green gas at RT

Very low solubility in water

56
Q

Physical properties of bromine

A

Brown volatile liquid at RT
Very high volatility
Slightly soluble in water

57
Q

Physical properties of iodine

A

Shiny black solid at RT
Sublimes with warming
Very very small solubility in water

58
Q

Advantages of batch

A

More versatile plant
More cost effective in small amounts
More applicable to slow reactions

59
Q

Disadvantages of batch

A

Less control over thermal energy
Contamination more likely
Larger workforce needed

60
Q

Advantage of continuous

A 
More suited to high tonnage production
Lower risk of contamination
Fine adjustments possible
Consistent quality ensured
Minimal about and easier automation
61
Q

Disadvantage of continuous

A

Much higher initial cost to build plant

Not cost effective below capacity

62
Q

Reactivity and oxidising ability of halogens

A

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
Q

What happens at electrodes during electrolysis of aqueous halid solution?

A

Formation of gas eg Cl2 or Br2 at positive

H2 at negative

64
Q

Silver chloride

A

White

65
Q

Silver bromide

A

Cream

66
Q

Silver iodide

A

Yellow

67
Q

Risks of transport and storage of halogens

A

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
Q

Uses of fluorine

A

PTFE, HCFCs, toothpaste

69
Q

Uses if chlorine

A

PVC and bleach

70
Q

Uses of bromine

A

Medicines, flame retardants

71
Q

Uses of iodine

A

Medicines, human nutrition

72
Q

Describe the preparation of a cholroalkane

A

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
Q

Describe and explain the principle stages in the preparation of an organic liquid product

A

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
Q

Characteristic properties of halogenoalkanes

A

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
Q

What’s hydrolysis?

A

Breaking of a bond by addition of water

76
Q

What’s substitution?

A

Where one group reacts to replace another group in a molecule

77
Q

What is a nucleophile?

A

Has a lone pair of electrons it can donate to a positively charged atom to form a covalent bond

78
Q

Reactivity of halogen compounds

A

C-F bond strongest so least reactive compound
C-I weakest so fairly reactive
Bond enthalpy shown to override bond polarity

79
Q

What is nitrate(v)?

A

NO3 -

80
Q

What is sulfate?

A

SO4 2-

81
Q

What is carbonate?

A

CO3 2-

82
Q

What is hydroxide?

A

OH -

83
Q

What is ammonium?

A

NH4 +

84
Q

What’s hydrogen carbonate?

A

HCO3 -

85
Q

Requirements of hydrogen bonding

A

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
Q

Solubility of polymers

A

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
Q

What’s a carboxylic acid?

A

R-COOH

Suffix -oic

88
Q

What’s an aldehyde?

A

R-COH

Suffix -al

89
Q

What is a ketone?

A

R-CO-R’

Suffix -one

90
Q

Difference between primary, secondary and tertiary alcohols?

A

Primary has one R group
Secondary has two R groups
Tertiary has three at groups

91
Q

Describe and explain heating under reflux

A

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
Q

What’s an elimination reaction?

A

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
Q

What is addition polymerisation?

A

Where smaller molecules join together to form one large molecule

94
Q

Test for unsaturation

A

Red-brown bromine water turns colourless

95
Q

Conditions for saturation of alkene

A

Alkene + Hydrogen
Nickel with heat and pressure (150*, 5atm.)(INDUSTRY)
Platinum and pressure at room temp (LAB)

96
Q

Conditions for hydration of alkene

A

Alkene + Water
Steam, phosphoric acid, heat and pressure (INDUSTRY)
Conc. sulphuric acid and water (LAB)

97
Q

Oxidation of alcohols

A

Require potassium dichromate(vi) solution
Primary to aldehyde then carboxylic acid
Secondary to ketone

98
Q

Dehydration of alcohol

A

Loses water to form an alkene
Al2O3 and heat (300*)
or H2SO4 and reflux

99
Q

What is an electrophile?

A

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
Q

How is the mechanism of addition supported experimentally?

A

Other anions which are present can be incorporated into the molecule

101
Q

Properties of polymers

A 
Chain length
Side groups
Branching
Stereo regularity
Chain flexibility
Cross-linking
102
Q

Effect of chain length in polymers

A

Longer = stronger

103
Q

Effect of side groups in polymers

A

Polar groups give stronger bonding so stronger polymers

104
Q

Effect of branching in polymers

A

Unbranched can get closer so bonding is stronger

105
Q

Effect of stereoregularity in polymers

A

Can pack closer when side groups orientated in a regular way, so stronger

106
Q

Effect of chain flexibility in polymers

A

More rigid is stronger

107
Q

Effect of cross-linking in polymers

A

Covalent bonds makes polymer harder and more difficult to melt

108
Q

What is a thermoplastic?

A

No cross links so can be melted and remoulded

109
Q

What is a thermoset?

A

Cross linked polymer, so doesn’t deform upon heating

110
Q

What’s a co-polymer?

A

Polymer made by addition of more than one kind of monomer

Chemistry (3 decks)

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