1. 1
   A student is asked to calculate the relative formula mass (Mr) of water, H2O, and carbon dioxide, CO2, using the relative atomic masses H = 1, C = 12 and O = 16.

   (a)

   What is the definition of relative formula mass?

   [1 mark]

   • AThe sum of the relative atomic masses of all the atoms shown in the formula of a compound
   • BThe mass of one atom of an element compared with hydrogen
   • CThe number of atoms in one mole of a substance
   • DThe mass, in grams, of one atom of a compound

   (b)

   Using Ar values H = 1 and O = 16, what is the relative formula mass of water, H2O?

   [1 mark]

   • A18
   • B17
   • C16
   • D34

   (c)

   Calculate the relative formula mass of carbon dioxide, CO2, showing your working.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student compares the relative formula mass of table salt, sodium chloride (NaCl), with limestone, calcium carbonate (CaCO3), using the relative atomic masses Na = 23, Cl = 35.5, Ca = 40, C = 12 and O = 16.

   (a)

   What is the relative formula mass of sodium chloride, NaCl?

   [1 mark]

   • A58.5
   • B23
   • C35.5
   • D81

   (b)

   How many oxygen atoms are shown in the formula of calcium carbonate, CaCO3, and so how many times must the Ar of oxygen be counted when calculating its Mr?

   [1 mark]

   • A3
   • B1
   • C2
   • D4

   (c)

   Calculate the relative formula mass of calcium carbonate, CaCO3, showing your working.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A pharmacist is calculating the relative formula mass of two compounds used in a laboratory: ethanoic acid, CH3COOH (molecular formula C2H4O2), and glucose, C6H12O6. Ar values: C = 12, H = 1, O = 16.

   (a)

   A pharmacist calculates the relative formula mass of two compounds. Calculate the relative formula mass of ethanoic acid, CH3COOH (molecular formula C2H4O2), using Ar values C = 12, H = 1 and O = 16, showing your working.

   [3 marks]

   (b)

   Calculate the relative formula mass of glucose, C6H12O6, showing your working, and explain why relative formula mass has no units.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A quality control chemist at a fertiliser factory checks the relative formula mass of two compounds used in fertiliser production: ammonium sulfate, (NH4)2SO4, and hydrated magnesium sulfate crystals, MgSO4.7H2O. Ar values: N = 14, H = 1, O = 16, Mg = 24, S = 32.

   (a)

   Using Ar values N = 14, H = 1, S = 32 and O = 16, calculate the relative formula mass of ammonium sulfate, showing full working and explaining how the brackets and subscripts in the formula are used in the calculation.

   [6 marks]

   (b)

   The chemist also checks hydrated magnesium sulfate crystals, MgSO4.7H2O. Using Ar values Mg = 24, S = 32, O = 16 and H = 1, calculate the relative formula mass of MgSO4.7H2O, showing full working and explaining how the water of crystallisation (the '.7H2O' part) is included in the calculation.

   [6 marks]

   Total for question 4: 12 marks

End of questions