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chemistry > topic 6 > Flashcards

topic 6 Flashcards

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1
Q

what is a general formula

A

algebraic formula that can be applies to the chemicals in the family
eg. CnH2n+2 alkanes

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2
Q

what is the molecular formula

A

actual number of atoms in a molecule
eg. ethane C2H6

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3
Q

what is the empirical formula

A

simplest whole number ratio of atoms in a compound
eg. ethane CH3

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4
Q

what is the structural formula

A

arrangement of atoms without showing all the bonds
eg. butan-1-ol CH3CH2CH2CH2OH

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5
Q

what is the skeletal formula

A

show bonds of carbon skeleton only
hydrogen and carbon not shown but functional groups are

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6
Q

what is the displayed formula

A

show arrangement of atoms showing all the bonds and atoms in the molecule

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7
Q

what is the homologous series

A

same functional group and general formula

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8
Q

how to name a molecule

A
  1. find length of stem by counting longest continuous chain of carbons
    meth eth prop but pent hex hept oct non dec
  2. functional group tells you ending of name
  3. number the carbon chain so functional group sits on the lowest number
  4. place number before suffix
  5. any side chains and less important functional groups are written as prefixes in alphabetical order
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9
Q

what is polymerisation

A

joining smaller monomers together to form a long chain

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10
Q

what is an addition reaction

A

joining molecules together to form longer ones

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11
Q

what is a hydrolysis reaction

A

splitting molecules into 2 using OH- or H+ to form a H2O molecule

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12
Q

what is a substitution reaction

A

replacing one atom with another on a molecule

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13
Q

what is reduction

A

when a species gains an electron in a reaction

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14
Q

what is oxidation

A

when a species loses electrons in a reaction

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15
Q

what is an elemination reaction

A

some atoms break away from larger molecule

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16
Q

what do arrows on mechanisms show

A

movement of electrons

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17
Q

what is nucleophilic substitution

A

primary halogenoalkanes and aq potassium hydroxide to make alcohols
amines made by reacting ammonia

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18
Q

what is radical substitution

A

reacting halogens to make alkanes to make halogenoalkanes

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19
Q

what is electrophilic addition

A

adding hydrogens and hydrogen halides to alkenes to make halogenoalkanes

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20
Q

what is chain isomerism

A

same molecular formula but different arrangement of the carbon skeleton

eg. pentane and 2-methylbutane

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21
Q

what is positional isomerism

A

same molecular formula but different position of functional group on carbon skeleton

eg. pentan-1-ol and pentan-2-ol

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22
Q

what is functional group isomers

A

same molecular formula but different functional group

eg. pent-1-ene and cyclopentane

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23
Q

what are alkanes and general formula

A

saturated hydrocarbons

Cn H2n+2

cycloalkanes CnH2n

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24
Q

what heterolytic fision

A

both electrons transfered to one species

for ions
X + and Y-

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25
Q

what is homolytic fission

A

form radicals
each species gets one electron

x. and Y.

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26
Q

what are the steps of free radical chain reactions

A

initiation
- radicals are produced normally using vissible light or UV, photochemical reactions
- bond breaks producing 2 radicals

prpagation
- radicals react with non radicals
- new radicals create which react with non radicals

termination
- two radicals react to form non radicals

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27
Q

draw free radical substitution of Cl2 and CH4

A

initiation
Cl —–Cl —-> Cl. + Cl.
UV

propagation
Cl. + CH4 –> .CH3 + HCl
.CH3 + Cl2 –> CH3Cl + Cl.

termination
Cl. + Cl. –> Cl2
.CH3 + .CH3 –> C2H6
.CH3 + Cl. –> CH3Cl

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28
Q

what happens in fractional distilation

A

column has temperature gradient
parts of hydrocarbon mixture condense at different temp beacuse of different chain lengths and bp
shorter hydrocatbons at top longer at bottom

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29
Q

what is cracking

A

heavier fractions can be cracked to higher demand lighter fractions

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30
Q

what is thermal cracking

A

high temp 1000 degrees and pressure 70atm
products mainly alkenes
make polymers

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31
Q

what is catalytic cracking

A

high temp 450 degree and slight pressure
zeolite catalyst lowers temp and pressure needed
lowers cost and speeds up process
product mainly aromatic hydrocarbons

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32
Q

how are cyclic and branched alkanes made in reforimg

A

using straight chain alkanes and platinum catalyst
straight chain alkanes create knocking and explode upon compression

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33
Q

what is the complete combustion of alkanes

A

form carbon dioxide and water

C4H10 (g) + 6.5 O2 (g) –> 4CO2 (g) + 5H2O (g)

34
Q

what is the incomplete combustion of alkanes

A

produce carbon monoxide and carbon (soot)

C4H10 + 4.5 O2 –> 4CO + 5H2O

C4H10 + 5.5O2 –> 2CO + 2CO2 + 5H2O

C4H10 + 2.5O2 –> 4C + 5H2O

35
Q

what is acid rain

A

release sulfur dioxide and oxides of nitrogen

sulfur dioxide - fossil fuels contrain sulfur based impurities–> acidic gas reacts with water in atmosphere to produce sulfuric acid

oxides of nitrogen - when nitrogen and oxygen are heated in engine –> dissolve in water in atmosphere to form nitric acid

36
Q

what do catalytic converters do

A

found mainly in vehicles to reduce harmful pollutants

convert carbon monoxide oxides of nitrogen and unburnt hydrocarbons to water vapour nitrogen and carbon dioxide

37
Q

what are fossil fuels

A

created from dead animals and plants that lived millions of years ago

coal
oil
gas

non renewable

38
Q

what are the biofuels

A

bioethanol, biodiesel, biogas

39
Q

how is ethanol made

A

sugar cane fermented

40
Q

what are the disadvantages of biofuels

A

ecpensive to convert existing petrol engines
land could be used to grow crops

41
Q

what are the advantages of biofuels

A

renewable so sustainable
carbon neutral, CO2 absorbed by plant, CO2 given off when burnt

42
Q

what are alkenes and general formula

A

unsaturated hydrocarbons
double bond
high electron density so reactive

CnH2n

43
Q

what is a sigma bond

A

2 s orbitals overlap
high bond enthalpy
strong electrostatic attraction between shared electrons and 2 nuclei due to high electron density

44
Q

what is a pi bond

A

overlap of 2 p orbitals
weaker than sigma as electron density spead out above and below
low bond enthalpy

45
Q

why are alkenes reactive

A

double bond has high electron density
4 electrons shared between bond
pi bond has low bond enthalp making it reactive
pi bond sticks out so open to attack from electrophiles

46
Q

what are stereoisomers

A

same structural formula but different arrangement of atoms in space

47
Q

what is e/z isomerism

A

E- same groups opposite the double bond
Z - same group on same side of double bond

48
Q

how to name stereoisomers

A
  1. label carbonds with double bond 1 and 2
  2. calculate atomic number of 1st element directly bonded to c=c, atom with highest atomic number given priority

if higher prioritys same sides z
if opposite e

49
Q

what happens to alkenes in electrophilic addition

A

attacked by electrophiles - electron pair acceptors defficient in electrons

curly arrow from double bond to E+

50
Q

what is the test for alkenes and mechanism

A

decolouration of bromine water
brown to colourless

see flash card

51
Q

what happens in the hydration of alkenes

A

alcohols produced
steam and acid catalyst used

ethene + water –> ethanol

52
Q

how to form diols from alkenes

A

using acidified potassium manganate (VII)
purple to colourless

ethene —H+/MnO4 - —> ethane-1,2-diol

53
Q

what happens to alkenes with the addition of hydrogen halides
draw mechanism

A

form halogenoalkanes

see flash card

54
Q

what happens when you react hydrogen halides with unsymertrical alkenes and what deterimes how much product is formed

A

produce 2 different products

amount dtermined by stability of carbocation

tertiary most stable as more electron pushing alkyl groups

55
Q

draw one repeat unit of propene

A

see flash card

double bonds broken
square brackets
n

56
Q

name and describe 3 ways plastics are disposed

A

landfill - plastics that are too difficult to recyle, too difficult to seperat, not enough plastic to extract to make it economically viable, not sustainable and increasingly expensive

recycle - plastics made from non renewable crude oil, cracked into monomers as organic feedstock or remoulded

incineration - burning to generate electricity, release toxic fumes

57
Q

what things should be considered when making sustainable polyers

A

reactants - environmentally friendly and not dangerous
solvents - little and low hazard like water
raw materials - renewable
energy - low as possible, catalyst used
waste - reduce waste products especially toxic and environmentaly harmful
longevity - make product out of a sustainable plastic

58
Q

what are biodegradable polymers and their advantages

A

decompose naturally in good supply of oxygen and mositure

made from crude oil fractions and renewable sources

  • crude oil not used
  • plant bassed polymers degrade and release CO2 which is absorbed by plant again
  • over products lifetime they use less energy to make than oil based
59
Q

how to name halogenoalkanes

A
  1. find longest carbon chain that will form the last part of the name
  2. the names and positions of halogens on molecule come first
    fluro- chloro- bromo- iodo-
  3. if you have more than one of the same tupe of halogen prefix with di tri tetra
60
Q

how do halogenoalkanes react with water

A

nucleophilic substitution
heat with water

alchol formed and H(Cl)

61
Q

what happens to the reactivity of halogenoalkanes

A

more reactive down and hydrolysed fastest

bond strength
halide ions get larger down group leading to weaker bond

62
Q

how to test reactivity of the halogens

A

add silver nitrate and ethnol

iodide - first - yellow precipitate
bromide - second - cream precipitate
chloride - third - white precipitate

63
Q

are primary or tertiary halogenoalkanes more reactive

A

tertiary more reactive

64
Q

how do halogenoalkanes react with nucleophiles and why

A

have a polar bond
attacked by nucleophiles - electron pair donor

attack delta+

65
Q

how do halogenoalkanes react with hydroxide ions
draw mechanism

A

conditions - warm aq sodium hydroxide under reflux

R–X + NaOH –> ROH + NaX

produce alcohol

OH- ion

see flash card

66
Q

how do halogenoalkanes react with cyanide ions
draw mechanism

A

conditions - warm ethanolic potassium cyanide under reflux

R–X + KCN –> RCN + KX

produce nitrile

-CN ion

see flash card

67
Q

how do halogenoalkanes react with ammonia
draw mechanism

A

conditions - heat with ethanoic ammonia excess ammonia

see flash card

68
Q

how do halogenolakanes react with ethanoic hydroxide ions

A

conditions - warm ethanoic sodium hydroxide under reflux

OH- acts as a base

produce alkene

see flash flash cards

69
Q

what are alcohols and genral formula

A

-OH

CnH2n+1 OH

70
Q

how to make chloroalkanes from alcohols

A

react with PCl5 or HCl

ROH + PCl5 –> RCl + HCl + POCl3

ROH + HCl –> RCl + H2O

71
Q

how to make bromoalkanes from alcohols

A

substitution

react with halide ion source eg. NaBr and acid catalyst

butan-2-ol + HBr –> 2-bromobutane + H2O

72
Q

how to make iodoalkanes from alcohols

A

react with PI3

3ROH + PI3 –> 3RI + H3PO3

73
Q

what happens in the dehydration of alcohols

A

alkenes made

acid catalyst used

see flash card

74
Q

what happens in the combustion of alcohols

A

produce carbon dioxide and water

C2H5OH + 3O2 –> 2CO2 + 3H2O

75
Q

what happens in the oxidation of primary alcohols

A

aldehydes the carboxylic acid

using potassium dichromate K2Cr2O7

see flash card

76
Q

what happens in the oxidation of secondary alcohols

A

ketones produced

potassium dichromate

77
Q

what happens in the oxidation of tertiary alcohols

A

not oxidised

78
Q

what is the test for aldehydes and ketones

A

fehlings or benedicts

aldehydes - blue to brick red

ketone - blue

79
Q

what is reflux

A

liebig condenser

hot evaporating substances hit cold condenser they turn back into liquid and return to round bottom flask

80
Q

what is distillation

A

separate substances with different bp

lower boiling point - colect in seperate vessel

higher bp - remain in round bottom flask

81
Q

what is redistilation and separation

A

redistilation - purify volatile substances

seperation - purify further

chemistry (15 decks)

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