Formulae, Equations and Amount of SubstanceEdexcel International A Level Chemistry: Topic test

1. 1
   A student studies hydrated copper(II) sulfate, CuSO₄·5H₂O. Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, Cu = 63.5.

   (a)

   What is the relative formula mass of hydrated copper(II) sulfate, CuSO₄·5H₂O?

   [1 mark]

   • A159.6
   • B249.6
   • C177.6
   • D231.6

   (b)

   What is the percentage by mass of water in hydrated copper(II) sulfate?

   [1 mark]

   • A56.4 %
   • B7.21 %
   • C63.9 %
   • D36.1 %

   (c)

   A student heats 5.00 g of the hydrated salt until all the water has been removed. Calculate the mass of anhydrous copper(II) sulfate that remains. Give your answer to 3 significant figures.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student dissolves a piece of aluminium foil of mass 0.540 g in excess dilute hydrochloric acid and makes the resulting aluminium chloride solution up to 250 cm³ with water. Relative atomic masses: Al = 27.0, Cl = 35.5. Avogadro constant L = 6.02 × 10²³ mol⁻¹.

   (a)

   How many aluminium atoms are in the piece of foil?

   [1 mark]

   • A1.20 × 10²²
   • B3.01 × 10²¹
   • C1.20 × 10²⁵
   • D8.78 × 10²⁴

   (b)

   What is the concentration of the aluminium chloride in the final solution?

   [1 mark]

   • A0.0216 mol dm⁻³
   • B5.00 × 10⁻³ mol dm⁻³
   • C0.0800 mol dm⁻³
   • D20.0 mol dm⁻³

   (c)

   Calculate the concentration of aluminium chloride, AlCl₃, in g dm⁻³. Give your answer to 3 significant figures.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student adds an excess of sodium sulfate solution to 25.0 cm³ of barium chloride solution of concentration 0.200 mol dm⁻³. A precipitate forms. Relative atomic masses: O = 16.0, S = 32.1, Ba = 137.3.

   (a)

   Write the full equation, with state symbols, and the ionic equation, with state symbols, for the reaction, and state what the student sees.

   [3 marks]

   (b)

   The precipitate is filtered, washed and dried. Its mass is 1.12 g. Calculate the theoretical yield of barium sulfate and hence the percentage yield.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Driver airbags inflate through the rapid decomposition of solid sodium azide: 2NaN₃(s) → 2Na(s) + 3N₂(g). Relative atomic masses: N = 14.0, Na = 23.0. Assume that nitrogen behaves as an ideal gas. R = 8.31 J K⁻¹ mol⁻¹.

   (a)

   An airbag must fill with 60.0 dm³ of nitrogen at 101 kPa and 300 K. Calculate the minimum mass of sodium azide needed. Give your answer to 3 significant figures.

   [6 marks]

   (b)

   In a test, 65.0 g of sodium azide produced 31.5 dm³ of nitrogen at 101 kPa and 300 K. Calculate the percentage atom economy for the production of nitrogen, and the percentage yield of nitrogen in the test. Comment on why a high percentage yield does not mean that the atom economy is high.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A workshop of volume 250 m³ is monitored for carbon monoxide, which must not exceed 35 ppm by volume. Take the molar volume of a gas as 24.0 dm³ mol⁻¹ and the molar mass of carbon monoxide as 28.0 g mol⁻¹.

   (a)

   What is the maximum volume of carbon monoxide that the air in the workshop may contain?

   [1 mark]

   • A0.875 dm³
   • B8750 dm³
   • C8.75 dm³
   • D8.75 m³

   (b)

   What is 35 ppm expressed as a percentage by volume?

   [1 mark]

   • A0.0035 %
   • B0.035 %
   • C0.35 %
   • D3.5 %

   (c)

   Calculate the mass of carbon monoxide present when the air is at the maximum permitted level. Give your answer to 3 significant figures.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   An organic compound extracted from fruit juice contains 40.0 % carbon, 6.7 % hydrogen and 53.3 % oxygen by mass. Its relative molecular mass is 180.0. Relative atomic masses: H = 1.0, C = 12.0, O = 16.0. Avogadro constant L = 6.02 × 10²³ mol⁻¹.

   (a)

   What is the empirical formula of the compound?

   [1 mark]

   • ACHO
   • BCH₂O
   • CC₂H₄O
   • DC₃H₆O₃

   (b)

   What is the molecular formula of the compound?

   [1 mark]

   • ACH₂O
   • BC₃H₆O₃
   • CC₁₂H₂₄O₁₂
   • DC₆H₁₂O₆

   (c)

   Calculate the number of molecules in 0.900 g of the compound.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   Chlorine water, Cl₂(aq), containing enough chlorine to oxidise all the iodide ions is added to 20.0 cm³ of colourless potassium iodide solution of concentration 0.150 mol dm⁻³. Relative atomic mass: I = 126.9.

   (a)

   Write the full equation, with state symbols, and the ionic equation, with state symbols, for the reaction, and state what is seen.

   [3 marks]

   (b)

   Calculate the maximum mass of iodine formed. Give your answer to 3 significant figures.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   Quicklime, CaO, is made by heating limestone: CaCO₃(s) → CaO(s) + CO₂(g). Relative atomic masses: C = 12.0, O = 16.0, Ca = 40.1. Assume that carbon dioxide behaves as an ideal gas. R = 8.31 J K⁻¹ mol⁻¹.

   (a)

   A sample of impure limestone of mass 25.0 g is heated until it stops losing mass. The carbon dioxide released has a volume of 5.40 dm³ at 101 kPa and 300 K. Calculate the percentage by mass of calcium carbonate in the sample, assuming that the impurities do not release any gas.

   [6 marks]

   (b)

   Calculate the percentage atom economy for making calcium oxide. A kiln operator heats 2.50 tonnes of pure calcium carbonate and obtains 1.28 tonnes of calcium oxide. Calculate the percentage yield, and suggest why the low atom economy need not make the process unsustainable.

   [6 marks]

   Total for question 8: 12 marks

End of questions