SL Paper 3
Nanotechnology has allowed the manipulation of materials on the atomic level.
Describe the structure and bonding of a carbon nanotube.
Structure:
Bonding:
Suggest one application for carbon nanotubes.
Proteins have structural or enzyme functions.
Oil spills are a major environmental problem.
Some proteins form an α-helix. State the name of another secondary protein structure.
Compare and contrast the bonding responsible for the two secondary structures.
One similarity:
One difference:
Explain why an increase in temperature reduces the rate of an enzyme-catalyzed reaction.
Suggest two reasons why oil decomposes faster at the surface of the ocean than at greater depth.
Oil spills can be treated with an enzyme mixture to speed up decomposition.
Outline one factor to be considered when assessing the greenness of an enzyme mixture.
Disposal of chemical waste is a growing problem in industry.
Outline the impact of antibiotic waste on the environment.
Suggest a concern about the disposal of solvents from drug manufacturing.
Consider the following data for butane and pentane at STP.
Discuss the data.
In a natural gas power station, 1.00 tonne of natural gas produces 2.41 × 104 MJ of electricity.
Calculate the percentage efficiency of the power station.
1 tonne = 1000 kg
Specific energy of natural gas used = 55.4 MJ kg−1
Enzymes are biological catalysts.
The graph shows the relationship between the temperature and the rate of an enzyme-catalysed reaction.
State one reason for the decrease in rate above the optimum temperature.
Explain why a change in pH affects the tertiary structure of an enzyme in solution.
State one use of enzymes in reducing environmental problems.
This question is about antiviral drugs.
Oseltamivir, used for the treatment of severe flu, is inactive until converted in the liver to its active carboxylate form.
Draw a circle around the functional group that can be converted to the carboxylate by hydrolysis.
Suggest a reason for using a phosphate salt of oseltamivir in oral tablets.
Anti-HIV drugs, such as zidovudine, often become less effective over time.
Explain the development of resistant virus strains in the presence of antiviral drugs.
This question is about nuclear reactions.
Fission of a nucleus can be initiated by bombarding it with a neutron.
Determine the other product of the fission reaction of plutonium-239.
Outline the concept of critical mass with respect to fission reactions.
Outline one advantage of allowing all countries access to the technology to generate electricity by nuclear fission.
State one advantage of using fusion reactions rather than fission to generate electrical power.
90Sr, a common product of fission, has a half-life of 28.8 years.
Determine the number of years for the activity of a sample of 90Sr to fall to one eighth () of its initial value.
Natural gas is an energy source composed mainly of methane.
Natural gas is burned to produce steam which turns turbines in an electricity generating power plant.
The efficiency of several sources for power plants is given below.
Calculate the specific energy of methane, in MJ kg−1, using sections 1, 6 and 13 of the data booklet.
Calculate the maximum electric energy output, in MJ, which can be obtained from burning 1.00 kg of methane by using your answer from (a).
Hydroelectric power plants produced 16 % of the world’s energy in 2015, down from 21 % in 1971.
Suggest why hydroelectric power production has a higher efficiency than the other sources given in (b) and why its relative use has decreased despite the high efficiency.
Reason for higher efficiency:
Reason for decreased use:
Methane can also be obtained by fractional distillation of crude oil.
Draw a circle on the diagram to show where the methane fraction is withdrawn.
List the following products, which are also obtained by fractional distillation, according to decreasing volatility: asphalt, diesel, gasoline, lubricating motor oil.
Explain how methane absorbs infrared (IR) radiation by referring to its molecular geometry and dipole moment.
Compare methane’s atmospheric abundance and greenhouse effect to that of carbon dioxide.
Polymers have a wide variety of uses but their disposal can be problematic.
Draw a section of isotactic polychloroethene (polyvinylchloride, PVC) showing all the atoms and all the bonds of four monomer units.
The infrared (IR) spectrum of polyethene is given.
Suggest how the IR spectrum of polychloroethene would differ, using section 26 of the data booklet.
Identify a hazardous product of the incineration of polychloroethene.
Explain how plasticizers affect the properties of plastics.
Suggest why the addition of plasticizers is controversial.
Metals are extracted from their ores by various means.
Aluminium is produced by the electrolysis of alumina (aluminium oxide) dissolved in cryolite.
Discuss why different methods of reduction are needed to extract metals.
Determine the percentage of ionic bonding in alumina using sections 8 and 29 of the data booklet.
Write half-equations for the electrolysis of molten alumina using graphite electrodes, deducing the state symbols of the products.
Anode (positive electrode):
Cathode (negative electrode):
The main fatty acid composition of cocoa butter and coconut oil is detailed below.
The melting points of cocoa butter and coconut oil are 34 °C and 25 °C respectively.
Explain this in terms of their saturated fatty acid composition.
Fats contain triglycerides that are esters of glycerol and fatty acids. Deduce an equation for the acid hydrolysis of the following triglyceride.
The addition of partially hydrogenated cocoa butter to chocolate increases its melting point and the content of trans-fatty acids (trans-fats).
Outline two effects of trans-fatty acids on health.
Powdered zinc was reacted with 25.00 cm3 of 1.000 mol dm−3 copper(II) sulfate solution in an insulated beaker. Temperature was plotted against time.
Estimate the time at which the powdered zinc was placed in the beaker.
State what point Y on the graph represents.
The maximum temperature used to calculate the enthalpy of reaction was chosen at a point on the extrapolated (dotted) line.
State the maximum temperature which should be used and outline one assumption made in choosing this temperature on the extrapolated line.
Maximum temperature:
Assumption:
To determine the enthalpy of reaction the experiment was carried out five times. The same volume and concentration of copper(II) sulfate was used but the mass of zinc was different each time. Suggest, with a reason, if zinc or copper(II) sulfate should be in excess for each trial.
The formula q = mcΔT was used to calculate the energy released. The values used in the calculation were m = 25.00 g, c = 4.18 J g−1 K−1.
State an assumption made when using these values for m and c.
Predict, giving a reason, how the final enthalpy of reaction calculated from this experiment would compare with the theoretical value.
A student investigated how the type of acid in acid deposition affects limestone, a building material mainly composed of calcium carbonate.
The student monitored the mass of six similarly sized pieces of limestone. Three were placed in beakers containing 200.0 cm3 of 0.100 mol dm−3 nitric acid, HNO3 (aq), and the other three in 200.0 cm3 of 0.100 mol dm−3 sulfuric acid, H2SO4 (aq).
The limestone was removed from the acid, washed, dried with a paper towel and weighed every day at the same time and then replaced in the beakers.
The student plotted the mass of one of the pieces of limestone placed in nitric acid against time.
[Source: © International Baccalaureate Organization 2019]
The student hypothesized that sulfuric acid would cause a larger mass loss than nitric acid.
Draw a best-fit line on the graph.
Determine the initial rate of reaction of limestone with nitric acid from the graph.
Show your working on the graph and include the units of the initial rate.
Explain why the rate of reaction of limestone with nitric acid decreases and reaches zero over the period of five days.
Suggest a source of error in the procedure, assuming no human errors occurred and the balance was accurate.
Justify this hypothesis.
The student obtained the following total mass losses.
She concluded that nitric acid caused more mass loss than sulfuric acid, which did not support her hypothesis.
Suggest an explanation for the data, assuming that no errors were made by the student.