O-LevelChemistryBonding & Structure5070/22 · Oct/Nov 2017 · Q710 Marks

The table shows the melting points and relative electrical conductivities of three elements from Period 3 of the Periodic Table. property element magnesium silicon sulfur melting point /°C 649 1410 113 relative electrical conductivity good conductor poor conductor does not conduct

(a)(i)Use ideas of structure and bonding to explain the difference in the melting points of magnesium and sulfur,[2]
(a)(ii)the difference in the electrical conductivity of magnesium and sulfur.[2]
(b)Silicon has a structure similar to diamond. Explain why silicon has a high melting point.[2]
(c)(i)A 40.5 g sample of a chloride of sulfur contains 21.3g of chlorine. Deduce the empirical formula of this chloride of sulfur. empirical formula[3]
(c)(ii)The relative molecular mass of this chloride is 135. Deduce the molecular formula of this chloride. molecular formula[1]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.

[1] Magnesium has strong bonding between positive ions / cations and electrons / magnesium is a giant structure
[1] Sulfur is a simple molecule / weak forces between sulfur molecules
[1] Magnesium has electrons which move (from place to place)
[1] Sulfur does not have delocalised electrons / no mobile electrons / electrons don't move
[1] Giant structure / many covalent bonds
[1] Need high temperature / lot of energy to break the bonds
[1] Mass of sulfur = 19.2 g
[1] mol S = 19.2/32 mol Cl = 21.3/35.5 OR ratio = 0.6 to 0.6
[1] SCl
[1] S2Cl2

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