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HSC Chemistry > Mod 7 > Flashcards

Mod 7 Flashcards

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1
Q

Properties of Alkanes

A

C-H bonds have weak temporary dipole-dipole forces (dispersion) as strongest intermolecular forces
General shape causes it to be non-polar
Low melting and boiling point
Insoluble in water
Poor conductor of electricity
Relatively stable and unreactive

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2
Q

Properties of Alkenes/Alkynes

A

Non-polar with dispersion forces
Unsaturated due to their bond type
More reactive (able to form extra bonds after breaking double/triple bonds)
Similar physical properties to alkanes

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3
Q

What are the different types of isomers (with explanation and examples)?

A

Chain Isomers are the rearrangement of carbon chain into different branches (Pentane, 2-Methylbutane, 2,2-Dimethylpropane)
Position Isomers is when basic carbon chain remains unchanged and functional groups move position (But-1-ene, But-2-ene)
Functional Group Isomers have the same molecular formula but different functional groups (Propanal, Propanone)

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4
Q

What are the different bond angles?

A

4 single bonds –> Tetrahedral –> 109.5
2 single bonds and 1 double bond –> Trigonal Planar –> 120
2 double bonds OR 1 single 1 triple –> Linear –> 180

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5
Q

What is a Homologous series?

A

A series of compounds with the same functional group and similar chemical properties (alcohols) (successive members differ by CH2)

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6
Q

What are the conditions of Hydrogenation?

A

Addition Reaction
Catalyst to Alkane is Palladium on Granulated Carbon (nickel, platinum alternatives)
Catalyst to Alkene is Palladium poisoned with Lead
Heat
Equations must be balanced

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7
Q

What are the conditions of Halogenation?

A

Halogen added to alkene or alkyne to produce haloalkene or haloalkane
no catalyst as halogens are very electronegative
room temperature

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8
Q

What are the conditions of Hydrohalogenation?

A

hydrogen halide delivered as gas not aqueous
no catalyst
room temperature

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9
Q

What are the conditions for Hydration?

A

alkene + h2o –> alcohol
catalyst is dilute H2SO4 or H3PO4
requires at least 160 degrees heat
for alkyne, ketone produced is much more thermodynamically favourably produced than alkane (isomer is then formed to alcohol since unstable)
catalyst for ALKYNE is sulfuric acid and mercury (II) sulfate catalyst (h2so4, hgso4)
heat 160 degrees at least too

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10
Q

What are the conditions for a substitution reaction?

A

saturated hydrocarbons (alkanes) replace a hydrogen with a halogen usually
energy needed to dissociate halogen is UV LIGHT
only 1 halogen can be substituted at a time and more reactions can occur subsequently with excess halogen
by product is hydrogen halide

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11
Q

What is the difference between primary secondary and tertiary alcohols

A

primary have 1 carbon chain (alkyl group) attached to the carbon that is adjacent to the OH functional group
secondary have 2 carbon chains (alkyl groups) attached to the carbon that is adjacent to the OH functional group
tertiary have 2 carbon chains (alkyl groups) attached to the carbon that is adjacent to the OH functional group

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12
Q

Combustion reactions of alcohols

A

highly exothermic
alcohol + oxygen –> co2 + h2o
requires initial input of energy to overcome activation energy (spark/heat)
complete –> excess or right amount of o2 converts all C to CO2
incomplete –> not enough o2 converts some C to CO or C solid (soot) (less energy per mole)

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13
Q

dehydration of alcohols

A

alcohol –> alkene + h2o
calalyst of concentrated h2so4, h3po4,al2o3
heat required for reasonable ROR for primary and secondary (for tertiary occur rapidly at room temp)
H and OH removed from 2 adjacent carbons to form double bond
primary –> 1 potential product
secondary –> 2 potential products (minor and major)

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14
Q

alcohol substitution with hydrogen halides

A

alcohol + hydrogen halide –> haloalkane + h2o
reactivity high to low –> tertiary, secondary, primary
oh group substituted for halogen
catalyst is aqueous hydrogen halide
another catalyst is ZnX2 where X is the substituting halogen

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15
Q

primary oxidation of alcohols

A

aldehydes are the first product since oh group on terminal
mild oxidant brings to aldehyde
strong oxidant brings to aldehyde then further to carboxylic/alkanoic acid (need double oxidant)
catalysts are: Acidified potassium dichromate (K2Cr2O7, Dilute H2SO4) Written as Cr2O72-/ H+ or H2SO4 . K2Cr2O7
Acidified potassium permanganate (KMnO4, Dilute H2SO4)
requires heat

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16
Q

secondary oxidation of alcohols + tertiary

A

catalyst can be either weak or strong oxidising agent
catalyst is Acidified potassium dichromate (K2Cr2O7, Dilute H2SO4)
Acidified potassium permanganate (KMnO4, Dilute H2SO4)
requires heat
oxidises to a ketone
does not further oxidise
tertiary cannot oxidise as there is no hydrogen attaches to associated hydroxyl carbon

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17
Q

Substitution of Halogenated organic compounds

A

Haloalkane + Dilute NaOH → Alcohol + Salt
catalyst is Dilute NaOH in acetone solvent (concentrated NaOH produces different products)
heat for fast ROR
halogen combines with Na to produce a salt
for tertiary, same conditions but different reaction: Tertiary Haloalkane + H2O → Tertiary Alcohol + HX
KEEP IN MIND ALCOHOL IS A PRODUCT

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18
Q

Alcohol Reaction with Na

A

primary alcohol + 2Na –> sodium alkoxide + h2 (very rapid)
secondary alcohol + 2Na –> no clue + h2 (mild)
tertiary alcohol + 2Na –> no clue + h2 (very slow)

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19
Q

environmental implications

A

drilling contaminates waterways and habitats, and land is needed so distrupts habitats, brings water laden with heavy metals to surface
contamination of water and soil, air and sound pollution, destruction of habitats
climate change when concentration of greenhouse gases in atmosphere increases and traps heat from radiating out of earth
gases are CO2 H2O CH4 (methane more potent and increasing)
linked to combustion of fossil fuels in cars being octane C8H18 + 25/2O2 –> 8CO2 + 9H2O
acid rain where ph of rain water is low caused by excessive emissions of oxides of nitrogen NxOy and sulphur dioxide SO2
causes acidification of lakes, erosion of stone and metal buildings, defoliation of forests and plant life
(ACID RAIN, AIR POLLUTION, THERMAL POLLUTION, DESTRUCTION OF NATURAL ECOSYSTEMS)

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20
Q

economic implications

A

economy heavily relies on hydrocarbons and fossil fuels being imported and exported for money (vital for economic growth through inflation)
used for electricity, heating, and cooling in households increasing quality of life
it is a readily available resource
it is cheap to produce

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21
Q

sociocultural implications

A

provides a steady income for individuals
increased availability for electricity
cheaper for households and general population to pay for to use
provides increased mobility for the community through public transport
poor working conditions sometimes which may constitute for human rights violations

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22
Q

test for combustion of alcohol

A

methanol –> blue flame –> complete combustion
ethanol –> blue and yellow flame –> incomplete combustion
pentan-1-ol –> yellow flame + soot –> even more incomplete combustion
as carbon chain increases, combustion decreases

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23
Q

test for reaction with sodium metal

A

add sodium metal to primary secondary tertiary alcohols and collect gas produced and test with burning split
ROR decreases in order Primary Secondary Tertiary
OH crowding causes less successful collisions

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24
Q

dehydration of sugar

A

put raw sugar in a beaker and cover with concentrated sulfuric acid
black mass formed

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25
Q

esters

A

add carboxylic acid to alcohol and heat in a water bath
then put in cold water to cool and smell it
H from alcohol combines with oh from carboxylic acid and makes water, with the c=o part of ester being from carboxylic acid
alcohol named first, replace ol with yl
carboxylic acid second, replace oic acid with anoate

26
Q

test to distinguish primary secondary tertiary alcohols

A

Lucas test–> lucat reagent is zinc chloride mixed with conc hcl
tertiary –> turbidity immediately
secondary –> turbidity in 1 to 10 mins
primary –> no turbidity

27
Q

properties of all alcohols

A

oh bond is polar and co bond is polar but not as polar as oh so cannot form hydrogen bonding
as length of carbon chain increases, bp/mp increases as molar mass increases and dispersion forces increase
alcohols have higher boiling point that corresponding alkanes as they are capable of dipole dipole and h bonding whereas alkanes arent
as length of carbon chain increases from 1-8 difference in bp from alkane and alcohol decreases as less proportion of molecule remains polar (dispersion force dominates)

28
Q

property difference of types of alcohols

A

different mp/bp due to accessibility of oh group
bp/mp decreases from primary secondary tertiary
oh crowding hinders formation of h bonding (the oh bonds are less accessible)

29
Q

solubility of alcohols

A

shorter chain alcohols mainly can act as a universal solvent due to their non-polar hydroxyl group and their polar alkyl group
Alcohols dissolve more readily in polar solvents than alkanes, but less reading in non-polar solvents than alkanes
length of chain increases, solubility in polar decreases (non polar alkyl chains associate with each other more)

30
Q

properties of aldehydes and ketones

A

dipole dipole forces with c=o bonds (no H bonding)
weaker bonds than alcohols as they have oh h bonding
polarity gives solubility in water and decreases as chain length increases (less than alcohols due to no h bonding)

31
Q

properties of carboxylic acids

A

2 highly electronegative oxygen atoms and are very polar
has all 3 types of bonding
highly soluble in water (esp shorter chains) decreases when chain length increases as non polar alkyl dominates
high boiling points
weak acids
more alkyl groups decreases acidity

32
Q

properties of amines

A

weaker intermolecular forces than alcohols and carboxylic acids
soluble in water typically short chained
has hydrogen bonding but n-h hydrogen bonding less than o-h as n is less electronegative
order of boiling points: tertiary<secondary<primary
primary have 2 nh bonds for h bonding, secondary have 1, tertiary have none (still has dipole dipole from c-n bonds)
weak bases (basicity increases with number of alkyl groups attaches to nitrogen) tertiary most basic, primary least basic
basic in gaseous, and a lot more basic in aqueous

33
Q

properties of amides

A

strongest intermolecular forces due to unique bonding geometry and extensive hydrogen bonding
very high boiling points
h bonding between n-h of one molecule and c=o of adjacent molecule
amides soluble in water but decreases when chain length, molecular mass and dispersion forces increase
neutral

34
Q

ester smells

A

ethyl butanoate –> pineapple
octyl ethanoate –> orange
pentyl ethanoate –> pear and banana
ethyl methanoate –> lemon, rum
ethyl heptanoate –> apricot
methyl butanoate –> apple

35
Q

properties of esters

A

2 polar bonds c-o c=o so dipole dipole and dispersion but NO H BONDING
lower bp than alcohols and carboxylic acid it is made from
poor solubility in water (lack of h bonding as water produces h bonding)
good solubility in non-polar
as chain length increases, dispersion forces increase and bp increases
as chain length increases, solubility in water decreases as hydrophobic alkyl chain dominates

36
Q

esterification

A

condensation rxn
requires conc h2so4 catalyst
requires heat (reflux) Reflux involves heating the chemical reaction for a specific amount of time, while continually cooling the vapour produced back into liquid form through a condenser tube into the reaction flask
18M h2so4 catlyst increases yield, and acts as dehydrating agent shifting equilibrium to the right
water is a solute that is dissolved in alcohol and carboxylic acid, meaning we can talk about water as concentration
reflux is used as heating causes loss of product due to volatility and alcohol is flammable

37
Q

benefits of reflux + extra esterifcation stuff

A

prevents loss of reagents and products, maximising yield
rxn can be perfomed at higher temps increasing ROR
improves safety be reducing risk of explosion and inhalation
use hotplate or heating mantle to reduce risk of naked flame
boiling chips for even mixing of solution

38
Q

purification of esters

A

neutralise excess acid (h2so4 or carboylic) with Na2CO3 or NaHCO3
add water to dissolve salts made after neutralising and excess water soluble substances (short chain alcohols)
put in separating funnel where denser aqueous substances like water and dissolved substanced are more dense and end up in bottom of the funnel
less dense organic layer with esters, and undissolved alcohols and carboxylic acids stays at top
add water again and again to dissolved more waste dissolved substances until required
distill remaining ester from remaining organic compounds
purity of ester can be tested with physical properties like bp, if bp is same or similar to true value, it is pure

39
Q

structure of surfactants (surface active agents)

A

soaps are natural, detergents are artificial
have a hydrophilic head: which is polar and often charged, interacting with water by ion-dipole or h bonding interactions
have a hydrophobic tail: which is non-polar and reacts with alkyl tails via dispersion forces (grease and fat and oil)

40
Q

soap

A

an ion with a long non polar alkyl tail and a polar charged carboxylate head
usually present as sodium or potassium salts

41
Q

anionic detergent

A

ion with a non-polar alkyl tail and polar anionic sulfate or benzenesulfanoate head
usually present as sodium or potassium salt
too harsh for personal hygiene, used in laundry detergent, dishwashing liquid, glass cleaner

42
Q

cationic detergent

A

ion with a long non-polar alkyl tail and a polar cationic trimethylammonium or quarternary ammonium head
usually present as chloride or bromine salts
not as harsh as anionic and are effective at removing static friction and tangling
used in shampoo and fabric softener
are biocidal which means they kill organisms so are used in disinfectants and antiseptics

43
Q

non-ionic detergent

A

long non-polar alkyl tail with polar repeating polyethylene glycol head
head is uncharged but still polar + ALWAYS ENDS IN ALCOHOL GROUP
less lather build up than anionic
used in shampoo and conditioner
used in front-loading washing machine for low sudsing, also used in some cosmetics

44
Q

how do soaps and detergents work

A

molecule acts on surface of water, hydrophilic head in water, hydrophobic tail out of water (monolayer formation)
some surfactant molecules dissolve in water and form micelles which are spherical arrangements (tail inwards favouring dispersion forces, head outward favouring ion-dipole/dipole-dipole with water on the outside)

45
Q

action of soaps and detergents (micellisation and agitation)

A

surfactant molecule dissolves in water
aligns so non-polar tail sticks into substance and polar head make ion-dipole forces with water
when surface is agitated (scrubbing), small droplets of grease/oil are lifted off dirty surface and suspended in water, this is when incomplete micelles are formed where tail is in substance but it is not spherical in shape
as oil droplets become smaller, micelles are formed

46
Q

action of soaps and detergents (emulsification)

A

entropy and enthalpy changes guide micellisation
micelles repel each other by spherical outer surface of negative or positive charges and dispersing throughout the water
this is called emulsification –> surfactant is emulsifier, final solution is an emulsion
2 normally immiscible substances (with each other like oil and water) are made to mix with the emulsifier (soap emulsifies oil and water)
when water is drained away, oil is taken with it, cleaning the surface

47
Q

carbon-neutrality

A

no net release of CO2
co2 emitted by complete combustion is matched by amount of CO2 emitted by original plant during photosynthesis

48
Q

biofuels

A

renewable fuels derived from plant material
renewable as plant matter they are made from is easily replenishable in a short timeframe through farming and harvesting

49
Q

bioethanol

A

is just ethanol and is called bioethanol as it it formed from the fermentatation of glucose obtained my natural sources such as cellulose or sugarcane to be used as fuel
cellulose from plant stalks or sucrose from sugarcane is digested in acid (moderately conc h2so4 or h3po4) to make glucose
glucose is fermented to ethanol and purified by distillation
max 15% w/v so when spirits or other higher w/v are needed, ethanol is distilled to separate from water to become more pure (at least 95% purity) (repeated multiple times with fractional for highest purity as water and ethanol have similar bp)

50
Q

fermentation

A

carbohydrates converted to alcohols by yeast and other microorganisms
alcohol tolerant yeast used to provide zymase enzyme to catalyst rxn
temp of 37 degrees maximises yield without damaging yeast
anaerobic environment: no oxygen, yeast must be deprived of oxygen, with oxygen it produces co2 and water
low pH of 3.7-4.6 by pumping is so2 to prevent pathogens from growing
maximum 15% w/v ethanol volume as ethanol kills the yeast

51
Q

what are the main chemical hazards

A

volatile easily forming vapour at room temp
flammable: low flashpoint that ignite at a low temperature
corrosive or caustic: capable of destroying solid material (can burn tissue)

52
Q

safe use of organic substances

A

ppe (lab coat, safety goggles, gloves (immediately disposed of after use)
fume cupboard while handling volatile or flammable substances
emergency shower and eye washer (irrigate/wash eyes for at least 15 minutes vigourously by holding open eyelids and moving eyes around)

53
Q

safe disposal of organic substances

A

sink drainage contaminates waterways
waste is segregated into categories: halogenated organic, non-halogenated organic, inorganic heavy metals, acidic/basic waste
acidic/basic neutralise with NaHCO3 to pH around 7 (then waste container)
heavy metal: place in heavy metal waste container
halogenated: place in halogenated organic waste container (more extensive treatment)
non-halogenated: place in non-halogenated organic waste container

54
Q

chemical spills

A

report to staff immediately
acid and base spills, use large amounts of nahco3 to neutralise (dont use water as it spreads spill)
large organic solvent spill, tell staff and evacuate immediately
wear face mask to clean

55
Q

bioethanol for fuels

A

100% pure ethanol is annhydrous but very hard to achieve and distillation is inadequate
bioethanol is a fuel additive for motor vehicle use
e10 fuel is 10 percent ethanol which is better for environment
25 percent ethanol fuel is used in brazil but blends beyond 10 percent are problematic as they require engine modications to work (expensive and limit market potential)

56
Q

why is ethanol good for fuel

A

co2 emitted from combustion same as co2 consumed by photosynthesis of sugarcane
addition co2 emitted when transporting ethanol however
lower enthalpy of combustion than octane so more is needed to produce same energy (negligible tho)
carbon neutral proof –> add photosyntheis fermentation and combustion

57
Q

biogas

A

mixture of methane and co2
made from organic waste materials previously consdiered useless so its cheap
reduces amount of waste in landfill
final waste can be used as fertiliser

58
Q

biodiesel

A

mixture of esters produced by reacting vegetable oil, palm oil or animal fat with base (undergoes esterification)
biodiesel can be used in standard diesel engines so any proportion of biodiesel can be used without engine modifications

59
Q

advantages of biofuels

A

renewable
carbon neutral
burns more cleanly than octane due to partially oxidised nature as it already has oxygen in its structure (reduces release of carbon monoxide-toxic gas)

60
Q

disadvantages of biofuels

A

technology relatively new so very expensive to produce
require environmental sacrifices to grow things like sugarcane
this reduce agricultural land for other crops
involves deforestation for more land destroying habitats and environment
pungent fermentation waste must be appropriately disposed
harvesting and distillation requires vast amounts of energy made by fossil fuels
engine modifications for biofuels could be costly

61
Q

evaluation of biofuels

A

imperative to develop further
not accepted into common usage due to economic and political unviability
good alt for future

HSC Chemistry (4 decks)

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