Jackson94
Member
- Joined
- Jun 5, 2010
- Messages
- 44
- Gender
- Male
- HSC
- 2012
Hey guy's here I will post some practice questions for this module, I will also post what I believe is the answer with the suggestion being that you guys possible learn from what I say and help improve the answers. These questions are either created by me or taken from textbooks that offer no answers so I am often forced to make up how many marks its worth.
1. Compare the processes of thermal cracking and catalytic cracking (4 marks)
Cracking of hydrocarbons involves turning long-chain hydrocarbons into shorter chain hydrocarbons, for example the cracking of ethane:
C2H6(g) -> C2H4(g) + H2(g)
Thermal cracking is the cracking of a long-chain hydrocarbon into shorter chain hydrocarbons by heating the hydrocarbons at very high temperatures. It is a highly endothermic process requiring large amounts of energy to break the covalent carbon-carbon bonds in the longer-chain hydrocarbon.
Catalytic cracking is similar but requires significantly lower temperatures because it uses a catalyst such as silicon and aluminum oxides or powdered zeolite. This can result in significant savings in both energy and therefor cost. So in short the only difference is that catalytic cracking requires a catalyst and thus lower temperatures while thermal cracking uses only heat and thus requires higher temperatures.
2. Explain how the structure of the zeolite catalyst assists in the process of cracking (2 Marks)
Zeolite, an aluminium silicate has many cavities and channels inside the porous catalyst which provides a high internal surface area for reaction. This reaction is hydrogen atoms being removed from the hydrocarbons forming a positive hydrocarbon ion that then undergoes further reactions. Overall the structure of zeolite helps lower the temperature needed for hydrocarbon cracking.
3. Write a balanced equation for the reaction in which propene undergoes vapor phase bromination in the presence of bromine molecules.
C3H6(g) + Br2(g) -> C3H5Br(g) + HBr(g)
4. A monomer is represented by the following condensed structural formula:
CHXCHY
where X and Y are functional groups
This monomer undergoes addition polymerisation. There are n repeating units in the final polymer. Draw an abbreviated structural formula for the polymer that forms.
(-CHXCHY-)n
5. Polymerisation can occur in two different ways. Distinguish between addition polymerisation and condensation polymerisation. (3 Marks)
-A polymer is a large-chain hydrocarbon made from repeating sub-units called monomers, polymerisation is the creation of this polymer from the monomer units.
For example the polymerisation of the ethylene monomer (C2H4)
(C2H4)n -> (-C2H4-)n
-Condensation polymerisation, also called step-growth involves monomers combining via a chemical process called condensation while eliminating a small molecule like water at each condensation step.
-Addition polymerisation is the creation of a polymer from monomers via an addition reaction.
-Thus although they both create polymers from monomer units, condensation polymerisation does it while emitting a small particle at each step and addition polymerisation does it without doing this.
1. Compare the processes of thermal cracking and catalytic cracking (4 marks)
Cracking of hydrocarbons involves turning long-chain hydrocarbons into shorter chain hydrocarbons, for example the cracking of ethane:
C2H6(g) -> C2H4(g) + H2(g)
Thermal cracking is the cracking of a long-chain hydrocarbon into shorter chain hydrocarbons by heating the hydrocarbons at very high temperatures. It is a highly endothermic process requiring large amounts of energy to break the covalent carbon-carbon bonds in the longer-chain hydrocarbon.
Catalytic cracking is similar but requires significantly lower temperatures because it uses a catalyst such as silicon and aluminum oxides or powdered zeolite. This can result in significant savings in both energy and therefor cost. So in short the only difference is that catalytic cracking requires a catalyst and thus lower temperatures while thermal cracking uses only heat and thus requires higher temperatures.
2. Explain how the structure of the zeolite catalyst assists in the process of cracking (2 Marks)
Zeolite, an aluminium silicate has many cavities and channels inside the porous catalyst which provides a high internal surface area for reaction. This reaction is hydrogen atoms being removed from the hydrocarbons forming a positive hydrocarbon ion that then undergoes further reactions. Overall the structure of zeolite helps lower the temperature needed for hydrocarbon cracking.
3. Write a balanced equation for the reaction in which propene undergoes vapor phase bromination in the presence of bromine molecules.
C3H6(g) + Br2(g) -> C3H5Br(g) + HBr(g)
4. A monomer is represented by the following condensed structural formula:
CHXCHY
where X and Y are functional groups
This monomer undergoes addition polymerisation. There are n repeating units in the final polymer. Draw an abbreviated structural formula for the polymer that forms.
(-CHXCHY-)n
5. Polymerisation can occur in two different ways. Distinguish between addition polymerisation and condensation polymerisation. (3 Marks)
-A polymer is a large-chain hydrocarbon made from repeating sub-units called monomers, polymerisation is the creation of this polymer from the monomer units.
For example the polymerisation of the ethylene monomer (C2H4)
(C2H4)n -> (-C2H4-)n
-Condensation polymerisation, also called step-growth involves monomers combining via a chemical process called condensation while eliminating a small molecule like water at each condensation step.
-Addition polymerisation is the creation of a polymer from monomers via an addition reaction.
-Thus although they both create polymers from monomer units, condensation polymerisation does it while emitting a small particle at each step and addition polymerisation does it without doing this.
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