1. 1
   A student weighs out 5.85 g of sodium chloride (Mr = 58.5) to dissolve in water and make a solution for an experiment.

   (a)

   What is the definition of one mole of a substance?

   [1 mark]

   • AThe relative formula mass of the substance expressed in grams
   • BThe mass of one atom of the substance in grams
   • CThe number of atoms in 1 g of the substance
   • DThe volume occupied by 1 g of the substance

   (b)

   Which equation should the student use to calculate the number of moles of sodium chloride weighed out?

   [1 mark]

   • An = m / Mr
   • Bn = Mr / m
   • Cn = m x Mr
   • Dn = m + Mr

   (c)

   Calculate the number of moles of sodium chloride in the 5.85 g sample, showing your working.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A lab technician needs to weigh out exactly 0.5 mol of calcium carbonate (Mr = 100) for an experiment.

   (a)

   What is the value of Avogadro's constant, which gives the number of particles in one mole of a substance?

   [1 mark]

   • A6.02 x 10^23
   • B1.00 x 10^0
   • C3.14 x 10^8
   • D9.11 x 10^-31

   (b)

   Which rearrangement of n = m/Mr should the technician use to calculate the mass of calcium carbonate needed for 0.5 mol?

   [1 mark]

   • Am = n x Mr
   • Bm = n / Mr
   • Cm = Mr / n
   • Dm = n + Mr

   (c)

   Calculate the mass of calcium carbonate the technician needs to weigh out to obtain 0.5 mol, showing your working.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student has an 8.8 g sample of carbon dioxide gas (Mr = 44) and wants to find out how many carbon dioxide molecules it contains.

   (a)

   Calculate the number of moles of carbon dioxide in this sample, showing your working.

   [3 marks]

   (b)

   Using your answer to part (a) and Avogadro's constant (6.02 x 10^23 particles per mole), calculate the number of carbon dioxide molecules present in the 8.8 g sample, showing your working and giving your answer in standard form.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A pharmaceutical quality control chemist is preparing and checking two samples in the laboratory: a batch of aspirin (Mr = 180) that must contain exactly 2.5 mol, and a cylinder of oxygen gas (Mr = 32) known to contain 3.01 x 10^24 molecules of O2.

   (a)

   A pharmaceutical quality control chemist needs to prepare a batch containing exactly 2.5 mol of aspirin (Mr = 180) for testing. Calculate the mass of aspirin needed, and the number of aspirin molecules this sample would contain, showing full working.

   [6 marks]

   (b)

   The chemist also has a cylinder known to contain 3.01 x 10^24 molecules of oxygen gas, O2 (Mr = 32). Calculate the number of moles of oxygen gas in the cylinder and the total mass of oxygen gas this represents, showing full working.

   [6 marks]

   Total for question 4: 12 marks

End of questions