Marking Scheme: Metals

This is the marking scheme for quiz: Metals

Section 1: Core Syllabus

Question 1

  • Good conductor of heat [1]
  • Good conductor of electricity [1]
  • Malleable / Ductile / High melting point / Lustrous (Any one) [1]

Question 2

  • A list of metals [1]
  • Arranged in order of their reactivity/decreasing reactivity [1]

Question 3 (a) Bright white light / intense white flame [1] (b) $2Mg(s) + O_2(g) \rightarrow 2MgO(s)$ [2] (1 for correct formula, 1 for balancing)

Question 4

  • Aluminum is more reactive than carbon [1]
  • Carbon cannot reduce aluminum oxide [1]

Question 5

  • Pure iron atoms are in regular layers that slide over each other [1]
  • Carbon atoms are different sizes, disrupting layers and preventing sliding [1]

Section 2: Extended Syllabus

Question 6

  • Reactivity increases down the group [1]
  • Outer electron is further from the nucleus/more shielding [1]
  • Weaker attraction between nucleus and outer electron, making it easier to lose [1]

Question 7 (a)

  • Blue solution fades/becomes colorless [1]
  • Red-brown solid deposits on zinc [1] (b)
  • Zinc is more reactive than copper [1]
  • Zinc atoms lose electrons (oxidation) [1]
  • Copper ions gain electrons (reduction) [1] (c) $Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s)$ [2]

Question 8

  • Chromium reacts with oxygen to form a thin, stable oxide layer [1]
  • This layer prevents further oxygen from reaching the iron [1]
  • Result: Steel becomes resistant to corrosion/rusting [1]

Question 9 (a) Coke burns to produce carbon dioxide, which then reduces to carbon monoxide; carbon monoxide reduces iron oxide to iron [2] (b) Limestone decomposes to calcium oxide, which reacts with sandy impurities (silica) to remove them as slag [2] (c) $Fe_2O_3(s) + 3CO(g) \rightarrow 2Fe(l) + 3CO_2(g)$ [2] (Accept other valid furnace equations)

Question 10

  • Iron is less reactive than aluminum [1]
  • Iron can be reduced by carbon (chemical reduction) [1]
  • Aluminum is highly reactive; only electrolysis can provide enough energy to reduce $Al_2O_3$ [2]