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(i) Give reasons for the following :
(I) Ionic compound have generally high melting points and boiling points.
(II) Solder, an alloy of lead and tin, is used for welding electrical wires.
(III) Carbon cannot reduce the oxides of $\ce{Na}$ or $\ce{Mg}$.
(ii) The reaction of compound ‘X’ with aluminium is used to join railway tracks :
(I) Identify the compound ‘X’.
(II) Name the reaction.
(III) Write the balanced chemical equation of the reaction of compound ‘X’ with aluminium.
(I) Ionic compound have generally high melting points and boiling points.
(II) Solder, an alloy of lead and tin, is used for welding electrical wires.
(III) Carbon cannot reduce the oxides of $\ce{Na}$ or $\ce{Mg}$.
(ii) The reaction of compound ‘X’ with aluminium is used to join railway tracks :
(I) Identify the compound ‘X’.
(II) Name the reaction.
(III) Write the balanced chemical equation of the reaction of compound ‘X’ with aluminium.
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(i) (I) A considerable amount of energy is required to break strong inter-ionic attraction. (1 Mark)
(II) Solder has low melting point. (1 Mark)
(III) Because Na or Mg have more affinity for oxygen than carbon. (1 Mark)
(ii) (I) $\ce{Fe2O3}$/ Iron (III) oxide (½ Mark)
(II) Thermit reaction (½ Mark)
(III) $\ce{Fe2O3(s) + 2Al(s) -> 2Fe(l) + Al2O3(s) + Heat}$ (1 Mark)
(Deduct ½ mark if no/ incorrect balancing)
(II) Solder has low melting point. (1 Mark)
(III) Because Na or Mg have more affinity for oxygen than carbon. (1 Mark)
(ii) (I) $\ce{Fe2O3}$/ Iron (III) oxide (½ Mark)
(II) Thermit reaction (½ Mark)
(III) $\ce{Fe2O3(s) + 2Al(s) -> 2Fe(l) + Al2O3(s) + Heat}$ (1 Mark)
(Deduct ½ mark if no/ incorrect balancing)