FT - 09 Structures and Bonding

FT - 09 Structures and Bonding

Q1.(a) PEX is a material that is used as an alternative to copper for hot water pipes.
PEX is made from poly(ethene).
(i)Describe how ethene forms poly(ethene).
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(2)
(ii)PEX is a shape memory polymer. What property does a shape memory polymer have?
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(1)
(iii)The simplified structures of poly(ethene) and PEX are shown.

Poly(ethene) is a thermoplastic that softens easily when heated.
Suggest and explain how the structure of PEX changes this property.
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(3)
(b) Copper is a suitable material to use for hot water pipes.PEX is now used as an alternative material for hot water pipes.
Copper is extracted from its ore by a series of processes.
1The low-grade copper ore is powdered and concentrated.
2The concentrated powdered copper ore is blown into a furnace with air to produce impure, molten copper. (This furnace is heated to 1100 °C using a hydrocarbon fuel.)
3Oxygen is blown into the impure, molten copper to remove any sulfur. The molten copper is cast into rectangular slabs.
4The final purification of copper is done by electrolysis.
PEX is made from crude oil by a series of processes:
•fractional distillation of crude oil
•cracking of naphtha fraction
•polymerisation of ethene
•conversion of poly(ethene) into PEX.
Use the information above and your knowledge and understanding to suggest possible environmental advantages of using PEX instead of copper for hot water pipes.
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(4)
(Total 10 marks)
HT - 09 Structures and Bonding
Q2.The diagram shows a ballpoint pen.

(a) Giveoneadvantage andonedisadvantage of recycling the materials from this type of ballpoint pen.
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(2)
(b) Alloys are used to make the ballpoint pen.
Givetworeasons why alloys are used in the ballpoint pen.
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(2)
(c) Decane (C10H22) can be used to produce poly(ethene).

(i)Describe the conditions needed forReaction 1.
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(2)
(ii)Describe, in terms of molecules, how poly(ethene) is produced inReaction 2.
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(2)
(d) Complete the displayed structure of the product in the equation.

styrenepoly(styrene)
(2)
(Total 10 marks)
M1.(a) (i)many ethene / molecules / monomers
accept double bonds open / break
accept addition polymerisation
1
join to form a long hydrocarbon / chain / large molecule
ignore references to ethane
correct equation gains2marks
1
(ii)(can be deformed but) return to their original shape (when heated or cooled)
ignore ‘it remembers its shape’
1
(iii)cross links / extra bonds in PEX
it = PEX throughout
accept inter-molecular bonds
ignore inter-molecular forces
1
molecules / chains in PEX are held in position
accept rigid structure
1
molecules / chains in PEX unable to slide past each other / move
1
(b) anyfourfrom:
ignore costs / sustainability / non-renewable
•less (hydrocarbon) fuels used
allow less energy
•less / no electrical energy used
allow no electrolysis
•reduce carbon / carbon dioxide emissions
allow less global warming
•reduce / no pollution by sulfur dioxide / acid rain
allow less / no transportation
•continuous process
•conserve copper which is running out or only low-grade ores available
allow less waste
•reduce the amount of solid waste rock that needs to be disposed
allow less mining
•reduce the need to dig large holes (to extract copper ores)
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M2.(a)anyoneadvantage from:
• conserves resources (of crude oil / metal ores)
ignore can be made into other items
allow the materials (in the pen) are non-renewable
allow less expensive than producing from the raw material
• reduces use of landfill
ignore less waste
•less use of fuels/energy
• less carbon dioxide produced
ignore global warming unqualified
1
anyonedisadvantage from:
• made of different polymers / alloys / materials
• difficulty / cost of separating the different materials
allow not all the materials can be recycled
1
(b) hard / strong / durable
1
resistant to corrosionorunreactive
allow do not rust
donotallow corrosive
1
(c) (i)vapours (of decane)
ignore pressure / hot / heat
allow high temperature (≥150 °C)
1
passed over a catalystorporous potoraluminium oxide
allow catalyst even if incorrectly named
1
or
mixed with steam (1)
at a (very) high temperature (1)
if temperature quoted, must be ≥ 500 °C
(ii)manymonomersormanyethene molecules
1
join / bond
allow addition polymerisation for second mark
1
OR
monomers / ethene molecules (1)
form chainsorvery large molecules (1)
if no other mark awarded allow double bond breaks / opens upordouble bond forms a single bond for1mark
(d)

allow bonds that do not extend through brackets
7 single bonds are used and are in the correct places with no additional atoms (1)
the brackets and the n are in the correct place (1)
2
[10]