Chemical Reactions and CalculationsIB MYP Chemistry: Topic test

1. 1
   A student in Brisbane heats aluminium powder strongly in oxygen. The silvery powder burns with a bright flame and forms white aluminium oxide, Al₂O₃. Her unbalanced equation is Al + O₂ → Al₂O₃. (Relative atomic masses: Al = 27, O = 16.)

   (a)

   Which is the correct balanced equation for this reaction?

   [1 mark]

   • AAl + O₂ → Al₂O₃
   • B2Al + 3O₂ → 2Al₂O₃
   • C4Al + 3O₂ → 2Al₂O₃
   • D2Al + O₂ → Al₂O₃

   (b)

   Two elements join to form a single compound in this reaction. Which type of reaction is it?

   [1 mark]

   • ASynthesis
   • BThermal decomposition
   • CNeutralisation
   • DPrecipitation

   (c)

   Calculate the relative formula mass of aluminium oxide, Al₂O₃.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Osaka weighs a pad of steel wool, which is iron, on a balance and then burns it in air. The reading rises from 5.00 g to 5.48 g. The iron reacts with oxygen to form iron(III) oxide: 4Fe + 3O₂ → 2Fe₂O₃.

   (a)

   Why does the mass reading increase?

   [1 mark]

   • AIron atoms are created during the reaction
   • BOxygen is destroyed during the reaction
   • CThe iron becomes less dense when it burns
   • DOxygen from the air joins the iron, so the product contains more atoms than the iron alone

   (b)

   What is the name for the change that happens to the iron when it gains oxygen?

   [1 mark]

   • AReduction
   • BOxidation
   • CNeutralisation
   • DThermal decomposition

   (c)

   The student repeats the experiment with the steel wool sealed in a flask on the balance. Explain why the mass reading stays the same.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A technician in Kolkata dissolves 5.30 g of anhydrous sodium carbonate, Na₂CO₃, in water and makes the solution up to 500 cm³ in a volumetric flask. (Relative atomic masses: Na = 23, C = 12, O = 16.)

   (a)

   Calculate the amount, in mol, of sodium carbonate that was dissolved.

   [3 marks]

   (b)

   Calculate the concentration of the solution in mol dm⁻³ and in g dm⁻³.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A fertiliser company in Hanoi makes ammonium sulfate, (NH₄)₂SO₄, by neutralising ammonia with sulfuric acid, and sells it to rice farmers. A quality inspector must confirm that a white powder delivered to a depot is ammonium sulfate. Farmers say the fertiliser raises rice yields, but a river-protection group says run-off from the fields harms local rivers.

   (a)

   Describe tests the inspector could carry out to show that the white powder contains both ammonium ions and sulfate ions. Include the results and an ionic equation for the sulfate test.

   [6 marks]

   (b)

   Discuss the benefits and drawbacks of using ammonium sulfate fertiliser on the rice fields, and reach a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A technician in Quito collects gases from three reactions. Gas P relights a glowing splint. Gas Q turns damp blue litmus paper red and then bleaches it white. Gas R burns with a squeaky pop when a lit splint is placed in it. The technician also needs to recognise ammonia and carbon dioxide.

   (a)

   Which row correctly identifies gases P, Q and R?

   [1 mark]

   • AP is hydrogen, Q is chlorine, R is oxygen
   • BP is oxygen, Q is chlorine, R is hydrogen
   • CP is oxygen, Q is hydrogen, R is chlorine
   • DP is chlorine, Q is oxygen, R is hydrogen

   (b)

   Which test identifies ammonia gas?

   [1 mark]

   • AIt relights a glowing splint
   • BIt turns limewater cloudy
   • CIt bleaches damp litmus paper
   • DIt turns damp red litmus paper blue

   (c)

   Describe the test for carbon dioxide gas and the result that shows it is present.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A diving instructor in Cairns checks two cylinders. Cylinder 1 holds 48 dm³ of oxygen gas, measured at room temperature and pressure. Cylinder 2 holds 2.0 mol of oxygen gas, O₂. At room temperature and pressure one mole of any gas has a volume of 24 dm³. (Relative atomic mass: O = 16. Avogadro constant = 6.0 × 10²³ per mol.)

   (a)

   How many moles of oxygen are in cylinder 1?

   [1 mark]

   • A2.0 mol
   • B0.50 mol
   • C72 mol
   • D1152 mol

   (b)

   What is the mass of oxygen in cylinder 2?

   [1 mark]

   • A16 g
   • B32 g
   • C64 g
   • D128 g

   (c)

   Calculate the number of oxygen molecules in cylinder 2.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A mining company in Western Australia extracts iron from haematite ore, which is mainly iron(III) oxide, Fe₂O₃. In a laboratory test a chemist reduces 80.0 g of pure iron(III) oxide with carbon monoxide: Fe₂O₃ + 3CO → 2Fe + 3CO₂. (Relative atomic masses: Fe = 56, O = 16, C = 12.)

   (a)

   Calculate the percentage by mass of iron in iron(III) oxide, Fe₂O₃.

   [3 marks]

   (b)

   Calculate the mass of iron produced from 80.0 g of iron(III) oxide, assuming the reaction goes to completion.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A food inspector in Kyoto checks the concentration of ethanoic acid, CH₃COOH, in vinegar by titration. She titrates 25.0 cm³ portions of diluted vinegar with sodium hydroxide solution of concentration 0.100 mol dm⁻³. One mole of ethanoic acid reacts with one mole of sodium hydroxide. The volumes of sodium hydroxide needed are 26.4 cm³ (a rough trial), then 24.9 cm³, 25.1 cm³ and 25.0 cm³. A new law may require every small vinegar producer to pay for regular testing like this. (Relative atomic masses: C = 12, H = 1, O = 16.)

   (a)

   Calculate the concentration of ethanoic acid in the diluted vinegar, in mol dm⁻³ and in g dm⁻³. Show which titres you use.

   [6 marks]

   (b)

   Discuss the benefits and drawbacks of requiring every small vinegar producer to pay for regular testing, and reach a justified conclusion.

   [6 marks]

   Total for question 8: 12 marks

End of questions