Relative formula mass and the moleIB MYP Chemistry: Subtopic test

1. 1
   A cement works in Turkey heats limestone, which is mostly calcium carbonate, CaCO₃. A chemist at the works calculates the amounts of substances being used. Relative atomic masses: Ca = 40, C = 12, O = 16.

   (a)

   What is the relative formula mass (Mr) of calcium carbonate, CaCO₃?

   [1 mark]

   • A68
   • B84
   • C100
   • D52

   (b)

   How many moles are there in 50 g of calcium carbonate?

   [1 mark]

   • A0.50 mol
   • B2.0 mol
   • C50 mol
   • D5000 mol

   (c)

   Calculate the mass of 3.0 mol of calcium carbonate.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A sports drink company in Australia lists glucose, C₆H₁₂O₆, as an ingredient and also uses large amounts of water, H₂O. Chemists count particles in moles. The Avogadro constant is 6.02 × 10²³ per mole. Relative atomic masses: H = 1, C = 12, O = 16.

   (a)

   Which statement best describes one mole of glucose?

   [1 mark]

   • AIt has a mass of 6.02 × 10²³ g
   • BIt contains 6.02 × 10²³ molecules of glucose
   • CIt is a single molecule of glucose
   • DIt has a mass of exactly 1 g

   (b)

   How many molecules are there in 2.0 mol of water?

   [1 mark]

   • A6.02 × 10²³
   • B3.01 × 10²³
   • C1.20 × 10²²
   • D1.20 × 10²⁴

   (c)

   Calculate the relative formula mass (Mr) of glucose.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A teacher gives students samples of four substances and asks them to weigh out one mole of each. The students record the mass of one mole: water, H₂O, 18 g; sodium chloride, NaCl, 58.5 g; magnesium oxide, MgO, 40 g; calcium carbonate, CaCO₃, 100 g. Relative atomic masses: H = 1, C = 12, O = 16, Na = 23, Mg = 24, Cl = 35.5, Ca = 40.

   (a)

   Describe the pattern in the data, verify it using one of the substances, and state a general rule.

   [3 marks]

   (b)

   A student uses the rule to find the mass of 0.25 mol of sodium chloride. She weighs out 14.8 g on a balance that reads to 0.1 g and claims that she has 0.25 mol. Calculate the mass expected and evaluate her claim.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A pharmaceutical company in Switzerland makes paracetamol tablets. Paracetamol has the formula C₈H₉NO₂. Each tablet must contain exactly the stated amount of paracetamol so that patients receive a safe dose, and chemists use moles to plan the amounts needed. The Avogadro constant is 6.02 × 10²³ per mole. Relative atomic masses: H = 1, C = 12, N = 14, O = 16.

   (a)

   A tablet contains 0.50 g of paracetamol. Calculate the relative formula mass of paracetamol, the number of moles in one tablet, and the number of molecules in one tablet.

   [6 marks]

   (b)

   Discuss whether governments should require every medicine manufacturer to check the amount of active substance in every batch using mass and mole calculations.

   [6 marks]

   Total for question 4: 12 marks

End of questions