HL Paper 3
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.
© International Baccalaureate Organization 2020
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.
Physical properties of elements vary according to atomic number. Sections 6 to 9 of the data
booklet list some of these properties.
Melting points and boiling points of elements 1 to 95
Deduce, giving a reason, the group of elements in the periodic table most likely to undergo sublimation.
Describe the density trend across periods 4 and 5 of the periodic table.
Suggest, with a reason, whether the lanthanoids or actinoids of the f-block would have the higher density.
Compare the ease of oxidation of s-block and d-block metals to their melting points and densities. Use section 25 of the data booklet.
Sketch how the first ionization energies of elements vary with their atomic radius.
