Chapter 5 Practice Paper: Formulae, equations and conservation of mass — question paper

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

1. 1

   The balanced equation for aluminium burning in oxygen is

   1. AAl + O₂ → AlO
   2. B4Al + 3O₂ → 2Al₂O₃
   3. C2Al + 3O₂ → Al₂O₃
   4. D3Al + O₂ → Al₃O₂
   ( )
2. 2

   In an equation, the label (aq) after a formula means the substance is

   1. Aa liquid element
   2. Ba gas
   3. Cdissolved in water
   4. Da wet precipitate
   ( )
3. 3

   A car engine burns fuel inside a sealed cylinder. The total mass of exhaust plus unchanged gases is

   1. Aequal to the mass of fuel plus air entered
   2. Bless than the fuel’s mass
   3. Cgreater than the fuel’s mass
   4. Dzero
   ( )
4. 4

   The relative formula mass of Mg(NO₃)₂ is (Mg 24, N 14, O 16)

   1. A86
   2. B134
   3. C168
   4. D148
   ( )
5. 5

   An oxide of sulfur contains 50% sulfur and 50% oxygen by mass (S 32, O 16). Its empirical formula is

   1. ASO
   2. BSO₂
   3. CSO₃
   4. DS₂O
   ( )
6. 6

   Which pair are both diatomic elements?

   1. ANitrogen and neon
   2. BChlorine and carbon
   3. COxygen and nitrogen
   4. DHelium and hydrogen
   ( )
7. 7

   Zinc displacing copper from solution is summarised ionically as

   1. AZn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
   2. BZn²⁺(aq) + Cu(s) → Zn(s) + Cu²⁺(aq)
   3. CSO₄²⁻(aq) → SO₄²⁻(aq)
   4. DZn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
   ( )
8. 8

   A burette reads to 0.1 cm³. The uncertainty of one reading is

   1. A±0.05 cm³
   2. B±0.1 cm³
   3. C±0.2 cm³
   4. D±1 cm³
   ( )
9. 9

   When 0.25 mol of carbon burns completely (C + O₂ → CO₂), the moles of CO₂ formed are

   1. A0.125 mol
   2. B0.25 mol
   3. C0.5 mol
   4. D1 mol
   ( )
10. 10

    Heating 4.2 g of a metal carbonate leaves 2.0 g of metal oxide and releases CO₂. The mass of CO₂ released is

    1. A2.0 g
    2. B4.2 g
    3. C2.2 g
    4. D6.2 g
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

1. 11

   Sodium reacts vigorously with water to give sodium hydroxide solution and hydrogen gas.

   1. (a)

      Give the balanced equation for sodium reacting with water, adding state symbols.

      [2]
   2. (b)

      A student seals the reaction in a rigid flask on a balance and repeats it. Predict the balance reading and explain.

      [2]
   3. (c)

      State the mole ratio of sodium to water in the reaction.

      [1]
2. 12

   A sample of a hydrocarbon contains 4.8 g of carbon and 1.0 g of hydrogen (C 12, H 1).

   1. (a)

      Calculate the empirical formula of the hydrocarbon.

      [3]
   2. (b)

      The hydrocarbon’s Mr is 58. Deduce its molecular formula and name it.

      [2]
   3. (c)

      Write the balanced equation for the complete combustion of this hydrocarbon.

      [1]
3. 13

   Two students investigate whether mass is conserved when hydrochloric acid reacts with sodium carbonate solution. Student A uses an open beaker; student B uses a sealed conical flask. Both start with 5.00 g of acid solution plus 1.06 g of sodium carbonate.

   Results

   Student	Vessel	Final reading / g
   A	Open beaker	5.88
   B	Sealed flask	6.06

   1. (a)

      Calculate the mass change student A observes and explain it.

      [2]
   2. (b)

      Explain why student B’s reading confirms conservation of mass.

      [2]
   3. (c)

      Write the balanced symbol equation for the reaction (Na₂CO₃ + HCl → NaCl + H₂O + CO₂).

      [2]
   4. (d)

      Use the equation to explain why the CO₂ released is 0.44 g when 1.06 g of Na₂CO₃ reacts fully (Na 23, C 12, O 16).

      [3]