WA2 Practice Paper: Weighted Assessment 2 — question paper

Section A: Multiple-choice questions[10 marks]

Answer all questions. For each question, write the letter (A, B, C or D) of the correct answer.

1. 1

   Magnesium chloride, MgCl₂, forms when magnesium atoms

   1. Atransfer two electrons, one to each of two chlorine atoms
   2. Bshare electrons with chlorine atoms
   3. Ctransfer one electron to one chlorine atom
   4. Dgain electrons from chlorine atoms
   ( )
2. 2

   The formula of aluminium oxide, built from Al³⁺ and O²⁻ ions, is

   1. AAlO
   2. BAl₃O₂
   3. CAlO₂
   4. DAl₂O₃
   ( )
3. 3

   Which property is typical of an ionic compound such as potassium chloride?

   1. Ait conducts electricity when solid
   2. Bit melts at a low temperature
   3. Cit conducts electricity when molten
   4. Dit evaporates easily
   ( )
4. 4

   A molecule of methane, CH₄, is held together by

   1. Aionic bonds only
   2. Bmetallic bonding
   3. Chydrogen bonds
   4. Dfour covalent bonds
   ( )
5. 5

   Water, H₂O, has a low boiling point for a compound even though its molecules contain strong covalent bonds. This is because

   1. Athe covalent bonds break on boiling
   2. Blittle energy is needed to separate one molecule from another
   3. Cwater is ionic
   4. Dhydrogen bonds are the strongest bonds known
   ( )
6. 6

   The relative formula mass of calcium hydroxide, Ca(OH)₂, is (Ca = 40, O = 16, H = 1)

   1. A57
   2. B58
   3. C74
   4. D75
   ( )
7. 7

   How many moles are there in 8.0 g of methane, CH₄? (H = 1, C = 12)

   1. A0.5 mol
   2. B2.0 mol
   3. C8.0 mol
   4. D128 mol
   ( )
8. 8

   One mole of any gas at room temperature and pressure occupies

   1. A24 cm³
   2. B24 dm³
   3. C12 dm³
   4. D1000 cm³
   ( )
9. 9

   In the reaction N₂ + 3H₂ → 2NH₃, the number of moles of hydrogen needed with 2 mol of nitrogen is

   1. A2 mol
   2. B3 mol
   3. C6 mol
   4. D8 mol
   ( )
10. 10

    A solution contains 0.25 mol of sodium hydroxide in 500 cm³ of solution. Its concentration is

    1. A0.125 mol/dm³
    2. B0.25 mol/dm³
    3. C5.0 mol/dm³
    4. D0.5 mol/dm³
    ( )

Section B: Structured questions[30 marks]

Answer all questions in the spaces provided. Show all necessary working.

1. 1

   Magnesium burns in chlorine to form magnesium chloride, an ionic compound.

   1. (a)

      State the electronic configuration of a magnesium atom (proton number 12) and of a chlorine atom (proton number 17).

      [2]
   2. (b)

      Describe, in terms of electron transfer, how magnesium chloride forms. Include the charges of the ions formed.

      [3]
   3. (c)

      State the formula of magnesium chloride.

      [1]
2. 2

   Sodium chloride melts at 801 °C; wax, a simple molecular solid, melts near 60 °C.

   1. (a)

      Explain, in terms of particles and forces, why so much more energy is needed to melt sodium chloride.

      [3]
   2. (b)

      Predict, with a reason, whether molten sodium chloride conducts electricity, compared with molten wax.

      [2]
3. 3

   Calcium carbonate, CaCO₃, decomposes when heated: CaCO₃ → CaO + CO₂. (Ca = 40, C = 12, O = 16)

   1. (a)

      Calculate the relative formula mass of CaCO₃.

      [1]
   2. (b)

      Calculate the number of moles in 25 g of calcium carbonate.

      moles =[2]
   3. (c)

      Calculate the number of moles of carbon dioxide produced when all 25 g decomposes, and the volume this gas occupies at room temperature and pressure.

      volume =dm³[3]
4. 4

   25.0 cm³ of sodium hydroxide solution is neutralised by 20.0 cm³ of 0.50 mol/dm³ hydrochloric acid: NaOH + HCl → NaCl + H₂O.

   1. (a)

      Calculate the moles of hydrochloric acid used.

      moles =[2]
   2. (b)

      State the moles of sodium hydroxide neutralised, with a reason from the equation.

      [1]
   3. (c)

      Calculate the concentration of the sodium hydroxide solution in mol/dm³.

      concentration =mol/dm³[3]
5. 5

   Zinc reacts with dilute hydrochloric acid: Zn + 2HCl → ZnCl₂ + H₂. (Zn = 65, H = 1, Cl = 35.5)

   1. (a)

      Write the full ionic equation for this reaction, including state symbols.

      [3]
   2. (b)

      Calculate the mass of zinc needed to make exactly 0.20 mol of hydrogen gas.

      mass =g[4]