Hey people, I've been looking at some past papers and many of them don't have answers. So I decided to post some attempted questions here please feel free to criticise me give me feedback.
1- Name a recently developed biopolymer and the organism or enzyme required to synthesis it. (2)
polyhydroxybutyrate (PHB) synthesised by Ralstonia eutropha by the enzymes Acetyl & PHB synthase
2-Evaluate the use or potential of the biopolymer relating it to it's properties. (3)
PHB is an important biopolymer to society as it is biodegradable and biodegradable ,decomposing in 2 years, allowing it to limit landfill and plastic caused pollution. It has good tensile strength, resistant to UV light with high melting point and premeable to oxygen whilst being biocompatible (the immune system doesn't reject it) so it can be used for bandaging, stitching and other medical applications. Unfortunately currently it's very expensive to produce and thus isn't the best choice for common plastic materials.
3- Define the term petrochemical industry.(1)
An industry based on production of plastics with use of petroleum products (oil and natural gas) and sever materials can be produced from common plastics to explosives.
4-GIve an example o fa compound associated with this industry. (1)
low density polethylene polymer
5. Justify the use of ethanol as an alternative fuel. (4)
Ethanol is used as an alternative fuel because it undergoes complete combustion burns much cleaner compared petrol, it's carbon neutral and unlike fossil fuel that need to mined and imported, it can be produced almost anywhere where plant matter grows. Because of fermentation of glucose (C6H12O6-->(anaerobic 37 degrees, zymase) 2CO2 + 2C2H5OH) ethanol can be produced from bio-matter (abundant to 7(10)^11 tonnes per annum) by hydration of cellulose into glucose. Because the ethanol source is biomatter the combustion and harvesting of ethanol is a cycle of producing CO2 and using it in photosynthesis to produce cellulose resulting in a carbon neutral cycle where no extra CO2 is released.
6- Describe a method used to produce transuranic elements.(2)
Transuranic elements are not naturally occurring elements after uranium the 92 element and are radioactive. Neutron bombardment in nuclear reactors is a method to obtain transuranic elements like neptunium where neutrons are released in the reactor by a fission chain reaction of mostly uranium-235. Then a the sample in lowered into the reactor where the neutrons bombard the sample making the element absorb it and become unstable resulting in a beta decay into the first few transuranic elements.
7- polyvinyl chloride and polystyrene are common polymers. Evaluate the use of each polymer in terms of their properties. (4)
Polyvinyl chloride is hard, non flexible polymer used for plumbing pipes and electrical wire coating. Because of it's water resistant and high tensile strength it's used as piping and as an insulator it's used for electrical wire coating. Alternatively polystyrene is used as an electrical and heat insulator and when in crystalline form it's high in toughness, rigidity and impact resistance thus used as tool handles, car battery case (electrical insulative property). When bubbled with air during production it's a foam structure with high heat insulative properties and therefore used as styrofoam cups.
8- Describe the procedure you undertook to calculate the molar heat of combustion for 3 named alkanols, per gram and per mole.(4)
1-collect sample of 3 alkanols, ie. methanol, ethanol, propanol
2-measure the mass of each alkanol (in their spirit burner) on an electronic weighing balance and record the mass.
3-measure the volume of 100 millilitres of water with a measuring cylinder.
4-clamp a empty metal container (emptied soft rink can) to a retort stand and place the 100 ml of water in it and also clamp a thermometer on the stand making sure the thermometer doesn't touch the container rather sitting in the middle of the water.
5-place the spirit burner for 1 alkanol under the metal can within 5 cm of wick
6-ignite the burner and record the time with a stopwatch.
7-remove the burner blowing out the flame when the temperature increases 10 degrees celsius.
8-measure and record the mass of the spirit burner and the alkanol in it.
9-wait for the calorimeter apparatus to cool and repeat this for the other 2 alkanols and repeat entire experiment 3 times.
SAFETY- Alkanols are extremely flammable, wear safety goggles and to prevent any accidents (i.e. dropping the spirit burner) by avoiding running and have all long hair tied back.
9- Name and give the formula of an amphiprotic species. (1)
hydrogen-carbonate/bicarbonate ion HCO3-
10- Use relevant equations to show why the species above is amphiprotic (2)
HCO3^- + H3O^+ --> H2CO3 + H2O, where the bicarbonate ion is accepting a proton
HCO3^- + OH^- --> CO3^-2 + H2O, where the ion is a proton doner
11- In one of the above eqautions underline the acid base conjugate pair. (1)
HCO3^- + H3O^+ --> H2CO3 + H2O , where H2CO3 is conjugate acid and HCO3^- is the base
12- Whose acid base theory is demonstrated in this question? (1)
Bronsted and Lowrey
13- Clearly explain the difference between the equivalance point and end point in titration. (2)
Equivilance point is where the moles of the unknown conc. solution equals the moles of the known solution. (no. moles of aliqot and titre equal). End point is the point where the indicator changes in colour and accordingly you stop the titration, the equvilance and end point can be made the same by choosing the right indicator.
14- CO(g) + Cl2(g) <--> COCl2 (g) H=-5kJ/mol
Explain what happens if there's a:
a) increased temperature
Due to le châtelier principal the equilibrium shifts to the left to negate the change and trying to cool the environment by absorbing heat (as forward reaction is exothermic) and favouring the backward reaction
b) removal of half of CO2
the concentration of the reactants (of forward reaction) decreases so to account for this the equilibrium shifts to the left to negate the change and thus reduce the COCL2 conc. trying to balance out the conc. of CO2.
c)Increase in volume
As the system's volume increase proportionally the pressure will decrease and mole ratio of the reactants to products is 2:1 so the negate the change the equilibrium will shift to the left to stabilise the pressure with more molecules of the reactants.
d) addition of a catalyst
Because an equilibrium reaction is where the rate of forward and reverse reaction are equal the addition of a catallyst will only accelerate both rates evenly and the catalyst only lowers the activation point to increase the rate of reaction. Hence the equilibrium won't shift and cause no change.
aaannnddd that's it for now, hope this helps to all those struggling like me.
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