C6.2 (2) Flashcards
define a polymer
large molecules built up from small units (or monomers)
how does addition polymerisation work?
in terms of bonds
- C=C double bond in alkenes is removed to produce a C-C single bond
- the bonds then join with unsaturated molecules to form a long saturated polymer
how do you produce an addition polymerisation reaction?
react alkenes together at high pressure and a catalyst
what is special about addition polymerisation reactions compared to condensation polymerisation?
- addition polymerisation only produces one product
how would you generally represent the product of an addition polymerisation reaction?
as a repeating unit (so the alkane , with two lines sticking out of the bracket), and a small n
- REMEMBER ALKANE NLY HAS ONE LINE BETWEEN THEM AS BONDS HAVE OPENED UP *
what does the polymer name depend on?
eg. if propene is monomer, what is the polymer name?
depends on the name of the monomer
- propene becomes poly(propene)
- MONOMER NAME REMAINS SAME, BUT BOND DIAGRAM DOES NOT*
what is an addition polymerisation reaction?
when (only 1 type of) small monomers (alkenes) join together to form one large polymer (saturated hydrocarbon chain)
what is a condensation reaction?
two molecules reacting together to produce one large molecule and a water molecule
how many functional groups must there be within a monomer for it to react? (during a condensation reaction)
- at least 2
how many monomers does each polymer (produced by a condensation reaction) usually contain?
100s or 1000s of monomers
what functional groups react together to produce a polyester?
(and how many of each one)
2 -OH groups (from alcohols) - HYDROXYL group
2 -COOH groups (from carboxylic acids) - CARBOXYL group
what are the produced when a polyester is formed?
- an ester group ‘‘-COO-“
- water
what functional groups react together to produce a polyamide? - and how many of each one ,k
(and what makes up an amide group)
2 carboxyl groups (-COOH)
2 animo groups (-NH2)
-CONH
what is a real life example of a polyamide?
a protein
explain how water is produced when a polyester is made
- OH lost off COOH group
- H lost of OH group
- CO and O join together to make a polyester
- OH and H lost join to form water
how do you represent a polymer after a condensation reaction?
draw repeating units with block diagrams (each block would represent a hydrocarbon group)
mainly draw repeating unit + n at the bottom
what 3 factors are needed to carry out a condensation reaction?
- high pressure
- high temperature
- with a catalyst
how would you produce a polyester in a school lab?
- heat together an alcohol + carboxylic acid
in presence of an acid catalyst
uses of polyesters?
clothing/fizzy drink bottles
ie. a polyester named PET
uses of polyamides?
clothing/ carpets
ie. polyamide named nylon
what is DNA?
a polymer made from four different monomers (called nucleotides)
what does a nucleotide (in DNA) consist of?
- a phosphate group (circle)
- deoxyribose sugar (pentagon)
- an organic base (rectangle)
what bond forms between opposite bases within DNA?
hydrogen bonds
how many naturally occuring proteins are there?
20
what does sucrose consist of?
simple sugars joined together (glucose + fructose)
what determines the reactions of organic compounds?
the generality of reactions of functional groups
BASICALLY FUNCTIONAL GROUPS CONTROL HOW ORGANIC COMPOUNDS REACT
define crude oil
a complex mixture of hydrocarbons (mainly alkanes)
why is crude oil able to be separated using fractional distillation?
as the different hydrocarbons that make up the mixture have different boiling points
how is crude oil made?
- from dead marine creatures
- pressure and temperature turned them into crude oil
explain (in terms of intermolecular forces), why fractional distillation is used to separate crude oil
- alkanes have different boiling points SINCE
- they have different numbers of carbon molecules (and therefore have different sized carbon chains)
- longer chained alkanes have a higher boiling point
- as the intermolecular forces between them are stronger
why do alkanes within crude oil have different boiling points?
- have different number of carbon molecules
- which affects chain length
- a longer chain length means intermolecular forces between them are stronger
- More energy is required to break these bonds
- and so has a high boiling point
what is the mnemonic to remember the name of the fractions?
licking
petrol
probably
does
harm
for
billy
describe the separation of crude oil by fractional distillation
- oil is heated in the fractioning column
- it evaporates
- hydrocarbons condense on designated fraction + are extracted
- each fraction contains substances with similar boiling points
which hydrocarbons have the lowest boiling points?
- refinery gases
ie. methane, ethane, propane, butane
(leaves through LPG at the top)
fractions are largely a ……… of compounds of formula …………. which are a member of the ……… homologous series
mixture, CnH2n+2, alkane
crude oil is the ……… source of …………… and is a …………… for the ……………….. industry
main, hydrocarbons, feedstock, petrochemical
how is modern life crucially dependant upon hydrocarbons?
each fraction obtained is used for something
ie. for plastics/oil/petrol
what is bitumen used for?
making roads
what is the paraffin fraction used for?
jet fuel
what kind of resource is crude oil?
finite resource
what is cracking?
a chemical reaction where large alkane molecules are converted to smaller alkene and alkane molevules
what are the conditions required for cracking to occur?
high temperature, catalyst, closed system
describe what happens in cracking?
- hydrocarbons (separated by fractional distillation) are
heated to a high temperature - then passed over a catalyst of alumina or silica
what bonds break during cracking?
the covalent bonds between the atoms (in large alkane molecules) break
why is cracking carried out?
- fractional distillation produces more long chained alkanes than short chained
- which are less useful
- cracking helps to produce more short chained (which are more useful)
what are small alkanes generally used for?
fuels
what are alkenes generally used for?
making plastic polymers
how does a chemical cell work?
produces a potential difference until the reactants are used up
give the advantages of hydrogen-oxygen fuel cells
- no combustion -> no greenhouse effects (only waste product is water)
- greater efficiency + is simple
- hydrogen and oxygen are abundant in the air
disadvantages of hydrogen-oxygen fuel cells
- need fossil fuels to produce hydrogen (not found by itself on earth)
- storage of hydrogen fuel is difficult
- hydrogen fuel is highly explosive
what is the word equation to model the chemical reaction occurring in a hydrogen-oxygen cell
hydrogen + oxygen -> water
how do hydrogen-oxygen fuel cells work?
- hydrogen enters cell
- it becomes oxidised at the anode (-)
- electrons lost then travel around the external circuit to the cathode (generating
electricity) - to the cathode (as there is a potential difference)
- hydrogen ions travel through the proton exchange membrane (a special membrane which allows only H+ through, not H^2 or O^2
- they then react with the oxygen coming from other inlet
- and produce water
what charges do each electrodes have in an hydrogen-oxygen fuel cell?
anode (-)
cathode (+)
- opposite to electrolysis
- electrons are always transferred from anode to cathode (in both electrolysis and fuel cells)
what are the order of fractions (shorter hydrocarbon chains -> longer).
LPG
Petrol
Paraffin
Diesel
Heating Oil
Fuel Oil
Bitumen
Licking petrol probably does harm for Billy
octane is separated lower down the fraction in column than methane. explain why, using ideas about intermolecular forces. (3)
any 3 from:
- octane is a longer-chained hydrocarbon
- longer-chained hydrocarbons have stronger IM forces than shorter-changed ones
- stronger IM forces means more energy required to break bonds
- octane has a higher boiling point (requires more energy)
- fractioning column is hotter at the bottom
not in markscheme but i think it’s important to understand:
- octane condenses lower down the column as it has a higher boiling point, so it cannot still be a gas at lower temps like methane
