POM 9.2.1 Flashcards
Acid + Metal —> ?
Salt + Hydrogen gas
Acid + Base —–> ?
Salt + Water
Acid + Carbonate –> ?
Carbon dioxide gas + salt + water
Cracking of PENTANE reaction
Pentane (g) –energy–> ethylene (g) + propane (g)
C5H12 (g) –energy–> C2H4 (g) + C3H8 (g)
Hydrogenation of ethylene
Ethylene (g) + Hydrogen (g) –Pt–> Ethane (g)
C2H4 (g) + H2 (g) –Pt–> C2H6 (g)
Hydration of ethylene
Ethylene (g) + H2o (l) –H3PO4–> Ethanol (l)
Dehydration of ethanol
Ethanol (l) –H2SO4–> Ethylene (g) + H2o (l)
C2H5OH (l) –H2SO4–> C2H4 (g) + H2o (l)
Fermentation of glucose
Glucose (aq) –yeast–> ethanol (aq) + carbon dioxide (g)
C6H12O6 (aq) –yeast–> 2C2H5OH (aq) + 2CO2 (g)
Displacement of Cu from solution due to Zn
Zinc + copper sulfate –> zinc sulfate + copper
Zn (s) + CuSO4 (aq) –> ZnSO4 (aq) + Cu (s)
Ionic equation of Cu and Zn displacement
Zn + Cu (II) sulfate ion + Sulfate ion –> Zinc (II) ion + sulfate ion + Cu
Zn + Cu 2+ + SO4 2- –> Zn 2+ + SO4 2- + Cu
Net ionic equation for displacement of Cu from Zn
Zinc + Copper (II) ion —> Zinc (II) ion + Copper
Zn (s) + Cu 2+ (aq) —> Zn 2+ (aq) + Cu (s)
Half-equations of displacement of Cu from Zn
- Zn —> Zn 2+ + 2e-
- Cu 2+ + 2e- —> Cu
Define an ALKANE
A hydrocarbon with only single bonds between the carbons
Define an ALKENE
A hydrocarbon with 1 or more double bonds between carbons
What is petroleum?
A complex mixture of hydrocarbons consisting mainly of alkanes and some alkenes
What is Ethylene? What is it’s systematic name and formula?
- Systematic name: Ethene
- Formula: C2H4
- One of the most useful substances in the petrochemical industry
- High demand
What is the process of CRACKING?
- The process of breaking large hydrocarbon molecules into smaller length chains, using heat (A)
- Catalytic cracking
- Thermal cracking
How is CRUDE OIL separated?
Fractional distillation
Describe CATALYTIC CRACKING
- Carried out in a “cat-cracker”
- Long ALKANE molecules (C15-C25) are broken into an ALKANE and an ALKENE
- Catalyst used: ZEOLITES
- Carried out at 500’C
- Absence of air
- Pressure above atmospheric pressure
- Uses less heat than thermal cracking but it is insufficient cause it can’t decompose large molecules completely
Describe THERMAL (steam) CRACKING
- No catalyst
- Alkanes are decomposed COMPLETELY
- Long-chain alkanes passed through metal tubes at 700’C - 1000’C
- Pressure above atmospheric
- Use of steam allows easy flow of hydrocarbon gases and removes carbon desposits
Why is ETHYLENE highly reactive?
- Ethylene has a highly reactive double-bond
- It is a site of high electron density
- One of the bonds readily breaks, creating 2 new bonding sites
What are ADDITION reactions?
- A type of reaction ethylene can undergo
- One bond in the double bond is broken and two atoms in a DIATOMIC molecule are ‘added on’
What are the different types of addition reactions?
- Hydrogenation: Ethylene + Hydrogen –Pt–> Ethane
- Hydration: Ethylene + Water –H3PO4–> Ethanol
- Halogenation: Reactive molecules from the halon group (Fl2, Cl2, Br2) can all react with ethylene
Describe POLYMERISATION
The chemical reaction in which many identical small molecules combine to form one large molecule
Differentiate between monomers and polymers
- Monomers are the small identical molecules
- A polymer is the large molecule formed from many monomers
Why can ethylene undergo polymerisation?
Because of its reactive double bond
What is the monomer and polymer in ethylene
- Monomer: Ethylene
- Polymer: Polyethylene
Describe Addition polymerisation
- No additional molecules are produced
- There is no gain/loss of atoms
- The double bond simply ‘opens’ and monomers attach
Describe the high pressure method in the production of polyethylene
- Ethylene subjected to pressures of 100-300MPa
- Temperatures of 300’C
- An initiator used (peroxide)
- Creates UNBRANCHED chains of polyethylene which does not pack together tightly
- LDPE
Describe the Ziegler-Natta Process in the production of polyethylene
- A few atmospheres of pressure
- Temperatures of 60’C
- Catalyst used
- Creates UNBRANCHED chains of polyethylene which pack together densely
- HDPE
What are the steps in the production of polyethylene?
- Initiation: the initiation molecule is added which reacts with one ethylene molecule, breaking the double bond and attaches to one bonding site, thus creating an ethylene initiator radical
- Propagation: Another ethylene monomer attaches to this radical and this continues
- Termination: The reaction stops when two such chains collide and the 2 radicals react, forming a longer chain
Describe Vinyl Chloride and it’s systematic name and formula
- Systematic name: Chloroethene
- Formula: C2H3Cl
- One hydrogen is substituted with a chlorine atom
- Can form Polyvinyl Chloride
Describe Styrene and it’s systematic name and formula
- Systematic name: Phenylethene
- Formula: C8H8
- One hydrogen atom replaced by a benzene ring
- Forms Polystyrene
Use of LDPE in relation to its properties?
Plastic cling wrap - it is flexible, clear and non-toxic
Use of HDPE in relation to its properties?
Rubbish bins - it is rigid, only slightly flexible and hard
Use of Polyvinyl Chloride (PVC) in relation to its properties?
Garden hoses - it can contain UV inhibitors, it’s flexible and is relatively un-reactive
Use of Crystal Polystyrene in relation to its properties?
CD cases - it is clear, hard, rigid, easily shaped and a good insulator
Use of Expanded Polystyrene in relation to its properties
Disposable cups - it is light, cheap and a thermal insulator
Which alkene and alkane were used to compare the reactivities of?
Cyclohexene and cyclohexane
What was the conclusion of the bromine water experiment?
- Cyclohexene turned the brome water colourless
- Cyclohexane solution remained yellow
- Thus, only cyclohexene reacted and therefore the alkene is said to be more active due to the double bond
Formula for the bromine water experiment
C6H10 (l) + Br2 (aq) + H2o (l) —–> C6h10BrOH (l) + HBr (aq)
Why was cyclohexene and cyclohexane used?
- Ethylene/propene weren’t used because C1 - C4 are gases at room temperature - hard to manage
- Cyclohexene is liquid at room temperature
Limitations of the bromine water test?
The alkane reacted slightly as UV radiation caused slow substitution reactions
Safety precautions of the bromine water experiment
- cyclohexene/ane are poisonous if ingested and both give off fumes as they are highly volatile and flammable (use in fume cupboard)
Limitations of the modelling of polymerisation practical
- The model only provided a limited section of a polyethylene molecule as there were limited numbers of kits
- The use of catalysts were not shown in the process - therefore less accurate
