Chapter 3 Practice Paper: Chemical Bonding and Structure — question paper

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

1. 1

   A magnesium atom (2.8.2) forms its ion by

   1. Alosing two electrons
   2. Bgaining two electrons
   3. Csharing two electrons
   4. Dlosing one electron
   ( )
2. 2

   The formula of the ionic compound formed between aluminium (Al³⁺) and oxide (O²⁻) is

   1. AAlO
   2. BAl₂O₃
   3. CAl₃O₂
   4. DAlO₂
   ( )
3. 3

   In a dot-and-cross diagram of water, each hydrogen atom achieves

   1. Aa full outer shell of eight electrons
   2. Ba positive charge
   3. Ctwo electrons in its only shell
   4. Dfour shared pairs
   ( )
4. 4

   Solid sodium chloride does not conduct electricity, but molten sodium chloride does. The explanation is that

   1. Athe ions are too heavy to move when solid
   2. Bsodium chloride decomposes when melted
   3. Celectrons flow through the molten salt
   4. Dmelting frees the ions to move and carry charge
   ( )
5. 5

   Brass is a mixture of copper and zinc. Brass is best described as

   1. Aa compound with a fixed formula
   2. Ban alloy of two metals
   3. Ca covalent molecule
   4. Dan ionic lattice
   ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided. Show all necessary working. Give numerical answers to 3 significant figures where appropriate, with units.

1. 1

   Sodium (2.8.1) reacts with chlorine (2.8.7) to form sodium chloride.

   1. (a)

      Describe, in terms of electrons, how each atom reaches a noble-gas arrangement.

      [3]
   2. (b)

      State the formula and charge of each ion formed.

      [1]
   3. (c)

      Describe the structure of solid sodium chloride.

      [2]
2. 2

   Draw described dot-and-cross diagrams (outer shells only) for the molecules below.

   1. (a)

      Describe the bonding in a molecule of hydrogen, H₂.

      [2]
   2. (b)

      Describe the bonding in a molecule of methane, CH₄.

      [2]
   3. (c)

      A molecule of CO₂ contains two double bonds. Describe what a double bond is.

      [2]
3. 3

   Substance A melts at 801 °C and conducts when molten but not as a solid. Substance B melts at −114 °C and never conducts. Substance C is shiny, conducts as a solid, and bends without breaking.

   1. (a)

      Classify A, B and C as ionic, covalent (molecular) or metallic, using the data.

      [3]
   2. (b)

      Explain why substance B has such a low melting point.

      [2]
4. 4

   Steel is an alloy of iron with a small amount of carbon. Cast iron contains more carbon than mild steel.

   1. (a)

      Describe how the arrangement of atoms in steel differs from that in pure iron.

      [2]
   2. (b)

      State one property that makes alloys useful instead of pure metals.

      [1]