ALS4SQ - Section 4 / Bonding and Structure II / P.1 (4.5 -...

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Section 4 / Bonding and Structure II / P. (4.5 - 4.7 Metallic bonding and The relationship between structures and properties of materials) / SKH Bishop Baker Secondary School AL Chemistry Section 4 Bonding and Structure II (4.5 - 4.7 Metallic bonding and The relationship between structures and properties of materials) 80 IIB Q.6 (a) The melting points and boiling points of the noble gases increase down the group. Why ? (2 marks) (b) Draw a diagram showing the variation down the series of the following : (i) The melting points of the fluoride, chloride and bromide of aluminium. (ii) The boiling points of the simplest hydrides of nitrogen, phosphorus and arsenic. (2 marks) (c) Carbon dioxide melts at - 57 o C (at 52 atmosphere) whereas silicon dioxide melts at 1700 o C (at 1 atmosphere). Why is there this great difference ? (Ignore the pressure.) (2 marks) 81 IA Q.2 (a) At room temperature, both oxygen and butane may be stored under pressure in steel cylinders. Under these conditions, oxygen is in the gaseous state, whereas butane is a liquid. Suggest an explanation for this difference. (2 marks) 81 IB Q.5 (c) Wet knitting wool stretches more than dry knitting wool. Suggest an explanation for this in terms of the changes in bonding which occur when knitting wool becomes wet. (2 marks) 81 IB Q.7 (a) Discuss the difference in the carbon-carbon distances in diamond and graphite. (5 marks) (b) It has been said that ‘pure ionic and pure covalent bonds only represent extreme bond types’. Do you agree with this statement ? Justify your answer. (7 marks) (c) Figure 1 above represents an ‘exploded’ view of a model of three layers of spheres on top of one another. Layer a is in contact with layer b , and layer b is in contact with layer c . If a fourth layer is placed on layer c so that the centres of the spheres are directly above the centres of the spheres in the first layer and the model is repeated, the sequence of the layers become abcabc 1
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Section 4 / Bonding and Structure II / P. (4.5 - 4.7 Metallic bonding and The relationship between structures and properties of materials) / (i) What type of packing does this model represent ? (1 mark) (ii) If the sequence is changed to abab , what type of packing would the model represent? (1 mark) (iii) What is the coordination number in both (i) and (ii) ? (1 mark) A unit cell for the abcabc arrangement is shown in Figure II. (iv) How many equivalent complete spheres can be considered to belong to the unit cell ?
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ALS4SQ - Section 4 / Bonding and Structure II / P.1 (4.5 -...

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