Amount of substanceAQA A-Level Chemistry: Topic test

1. 1
   A pharmacy technician is checking a 500 mg paracetamol tablet. Paracetamol has the molecular formula C₈H₉NO₂. Relative atomic masses: C 12.0, H 1.0, N 14.0, O 16.0. The Avogadro constant is 6.02 × 10²³ mol⁻¹.

   (a)

   What is the relative molecular mass of paracetamol?

   [1 mark]

   • A151.0
   • B135.0
   • C119.0
   • D137.0

   (b)

   How many moles of paracetamol are there in one 500 mg tablet?

   [1 mark]

   • A3.31
   • B3.31 × 10⁻⁶
   • C3.31 × 10⁻³
   • D1.51 × 10²

   (c)

   Calculate the number of oxygen atoms in one tablet.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An aerosol can of volume 250 cm³ contains propane gas, C₃H₈, at a temperature of 25 °C and a pressure of 3.00 × 10⁵ Pa. The gas constant, R, is 8.31 J K⁻¹ mol⁻¹. Relative atomic masses: C 12.0, H 1.0.

   (a)

   What volume should be used for the can in the ideal gas equation, in m³?

   [1 mark]

   • A2.50 × 10⁻⁷
   • B2.50 × 10⁻⁴
   • C2.50 × 10⁻¹
   • D2.50 × 10²

   (b)

   How many moles of propane are in the can?

   [1 mark]

   • A30.3
   • B3.03 × 10⁻⁵
   • C0.361
   • D3.03 × 10⁻²

   (c)

   Calculate the mass of propane in the can.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A compound Y, used to make nylon, contains only carbon, hydrogen and oxygen. Analysis shows that Y contains 49.3% carbon, 6.8% hydrogen and 43.9% oxygen by mass. The relative molecular mass of Y is 146.0. Relative atomic masses: C 12.0, H 1.0, O 16.0.

   (a)

   Calculate the empirical formula of Y.

   [3 marks]

   (b)

   Determine the molecular formula of Y. Write a balanced equation for the complete combustion of Y, then calculate the mass of carbon dioxide produced when 1.46 g of Y burns completely. (Relative formula mass of CO₂ = 44.0.)

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Ethanoic acid, CH₃COOH, is the acid in vinegar. A student finds the concentration of ethanoic acid in a vinegar by titration. A 25.0 cm³ sample of the vinegar was diluted to 250 cm³ in a volumetric flask, and 25.0 cm³ portions of the diluted solution were titrated with 0.100 mol dm⁻³ sodium hydroxide, giving a mean titre of 22.40 cm³. Industrially, ethanoic acid is made by two routes. Route 1: CH₃OH + CO → CH₃COOH. Route 2: C₂H₅OH + O₂ → CH₃COOH + H₂O. Relative formula masses: CH₃OH 32.0, CO 28.0, C₂H₅OH 46.0, O₂ 32.0, CH₃COOH 60.0.

   (a)

   Write an equation for the reaction between ethanoic acid and sodium hydroxide. Calculate the concentration of ethanoic acid in the vinegar, in mol dm⁻³ and in g dm⁻³.

   [6 marks]

   (b)

   In a trial of route 2, 2.30 kg of ethanol produced 2.04 kg of ethanoic acid. Calculate the percentage atom economy of each route and the percentage yield in the trial. Evaluate which route the company should prefer.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   Limestone contains calcium carbonate, which reacts with hydrochloric acid: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. A student reacts 4.00 g of calcium carbonate with an excess of the acid. The relative formula mass of CaCO₃ is 100.1. The gas constant, R, is 8.31 J K⁻¹ mol⁻¹.

   (a)

   How many moles of carbon dioxide are produced?

   [1 mark]

   • A0.0200
   • B0.0800
   • C0.0400
   • D0.400

   (b)

   What volume of carbon dioxide is produced at 298 K and 100 kPa?

   [1 mark]

   • A0.990 dm³
   • B0.0990 dm³
   • C1.98 dm³
   • D0.990 m³

   (c)

   Calculate the volume of 1.00 mol dm⁻³ hydrochloric acid needed to react exactly with the 4.00 g of calcium carbonate.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   Bone mineral is largely calcium phosphate, Ca₃(PO₄)₂. A forensic scientist analyses samples of bone. Relative atomic masses: Ca 40.1, P 31.0, O 16.0. The Avogadro constant is 6.02 × 10²³ mol⁻¹.

   (a)

   What is the relative formula mass of calcium phosphate, Ca₃(PO₄)₂?

   [1 mark]

   • A135.1
   • B215.3
   • C246.3
   • D310.3

   (b)

   Another mineral sample contains 38.8% calcium, 20.0% phosphorus and 41.2% oxygen by mass. What is its empirical formula?

   [1 mark]

   • ACa₃P₂O₄
   • BCa₃P₂O₈
   • CCaPO₄
   • DCa₂PO₄

   (c)

   A bone sample contains 2.00 g of Ca₃(PO₄)₂. Calculate the number of calcium ions in the sample.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A laboratory burns 3.00 g of methane, CH₄, completely, using exactly the amount of oxygen needed: CH₄ + 2O₂ → CO₂ + 2H₂O. All gas volumes are measured at 400 K and 100 kPa, at which water is a gas. Relative atomic masses: C 12.0, H 1.0, O 16.0. The gas constant, R, is 8.31 J K⁻¹ mol⁻¹.

   (a)

   Calculate the volume of oxygen needed, in dm³, at 400 K and 100 kPa.

   [3 marks]

   (b)

   Calculate the mass of water produced and the total volume of gas present after the combustion, at 400 K and 100 kPa.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A 0.750 g sample of an organic compound Z, containing only carbon, hydrogen and oxygen, is burned completely in excess oxygen. It gives 1.100 g of carbon dioxide and 0.450 g of water. The relative molecular mass of Z, from its mass spectrum, is 90.0. Z is made industrially by fermenting glucose, C₆H₁₂O₆ (relative formula mass 180.0), which gives Z as the only product. Relative formula masses: CO₂ 44.0, H₂O 18.0. Relative atomic masses: C 12.0, H 1.0, O 16.0.

   (a)

   Calculate the empirical formula and the molecular formula of Z.

   [6 marks]

   (b)

   Z has the molecular formula C₃H₆O₃. In one batch, 36.0 kg of glucose gave 28.8 kg of Z, which was dissolved to make 500 dm³ of solution. Write a balanced equation for the fermentation. Calculate the percentage yield, state the percentage atom economy with a reason, and calculate the concentration of Z in the solution in mol dm⁻³.

   [6 marks]

   Total for question 8: 12 marks

End of questions