HL Paper 3
Nuclear reactions transform one nuclide into another. Fission, splitting a large nucleus into two smaller nuclei, releases vast amounts of energy.
(i) Uranium hexafluoride, UF6, is used in the uranium enrichment process that produces fuel for nuclear reactors.
State the molecular shape of uranium hexafluoride.
(ii) Explain why uranium dioxide, UO2, has a very high melting point whereas uranium hexafluoride vapourises easily into gas.
There has been significant growth in the use of carbon nanotubes, CNT.
Explain these properties of carbon nanotubes.
CNT can act as Type 2 superconductors. Outline why Type 2 superconductors are generally more useful than Type 1.
Explain the role of electrons in superconducting materials in terms of the Bardeen–Cooper–Schrieffer (BCS) theory.
Alloying metals changes their properties. Suggest one property of magnesium that could be improved by making a magnesium–CNT alloy.
Pure magnesium needed for making alloys can be obtained by electrolysis of molten magnesium chloride.
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Calculate the theoretical mass of magnesium obtained if a current of 3.00 A is used for hours. Use charge :(Q) = current (I) × time (t) and section 2 of the data booklet.
Suggest a gas which should be continuously passed over the molten magnesium in the electrolytic cell.
Zeolites can be used as catalysts in the manufacture of CNT. Explain, with reference to their structure, the high selectivity of zeolites.
Experiments have been done to explore the nematic liquid crystal behaviour of CNT. Justify how CNT molecules could be classified as nematic.
Low density polyethene (LDPE) and high density polyethene (HDPE) are both addition polymers.
Describe how the monomers of addition polymers and of condensation polymers differ.
Identify the type of intermolecular bonding that is responsible for Kevlar®’s strength.
Proteins are polymers of amino acids.
A paper chromatogram of two amino acids, A1 and A2, is obtained using a non-polar solvent.
© International Baccalaureate Organization 2020.
Determine the value of A1.
Proteins are polymers of amino acids.
The mixture is composed of glycine, , and isoleucine, . Their structures can be found in section 33 of the data booklet.
Deduce, referring to relative affinities and , the identity of A1.
Proteins are polymers of amino acids.
Glycine is one of the amino acids in the primary structure of hemoglobin.
State the type of bonding responsible for the α-helix in the secondary structure.
Proteins are polymers of amino acids.
Sketch and label two oxygen dissociation curves, one for adult hemoglobin and one for foetal hemoglobin.
Proteins are polymers of amino acids.
Explain why the affinity for oxygen of foetal hemoglobin differs from that of adult hemoglobin.
DNA, deoxyribonucleic acid, is made up of nucleotides.
List two components of nucleotides.
Explain how the double-helical structure of DNA is stabilized once formed.
Aspirin is formed by reacting salicylic acid with ethanoic anhydride. The structure of aspirin is given in section 37 of the data booklet.
Deduce the structural formula of the by-product of this reaction.
Aspirin crystals are rinsed with water after recrystallization to remove impurities.
Suggest why cold water is used.
The solubility of aspirin is increased by converting it to an ionic form. Draw the structure of the ionic form of aspirin.
Comment on the risk of overdose when taking aspirin as an analgesic, referring to the following values, for a person weighing :
Minimum therapeutic dose
Estimated minimum lethal dose
Explain how IR spectroscopy can be used to distinguish aspirin from salicylic acid.
Solubility plays an important role in the bioavailability of drugs in the body.
Suggest why aspirin is slightly soluble in water. Refer to section 37 of the data booklet.
A student prepares aspirin from salicylic acid in the laboratory, extracts it from the reaction mixture, ensures the sample is dry and determines its melting point.
Suggest why the melting point of the student’s sample is lower and not sharp compared to that of pure aspirin.
Organic molecules can be characterized using infrared (IR) spectroscopy.
Compare and contrast the infrared peaks above 1500 cm−1 in pure samples of aspirin and salicylic acid using section 26 of the data booklet.
Some mild analgesics contain a solid mixture of acidic aspirin and a non-acidic organic chemical of similar polarity to asprin.
Discuss how acid-base properties and the process of solvent extraction can be used to separate aspirin from the mixture.
The pharmaceutical industry is one of the largest producers of waste solvents.
State a green solution to the problem of organic solvent waste.
Describe the function of chlorophyll in photosynthesis.
Compare and contrast the structures of starch and cellulose.
One similarity:
One difference:
Explain why maltose, C12H22O11, is soluble in water.