Relative masses and the moleAQA A-Level Chemistry: Mind map

Exam questions on Relative masses and the mole

1. Magnesium nitrate, Mg(NO₃)₂, is used in some fireworks as an oxidising agent. A technician needs to convert between masses and amounts of this compound, using relative atomic masses Mg 24.3, N 14.0 and O 16.0.
   Calculate the amount, in mol, of magnesium nitrate in 7.42 g of Mg(NO₃)₂. Give your answer to 3 significant figures.2 marks
2. A student has 3.60 g of water, H₂O, in a beaker. Use relative atomic masses H 1.0 and O 16.0, and the Avogadro constant, 6.02 × 10²³ mol⁻¹.
   Calculate the mass, in grams, of one molecule of water. Give your answer in standard form to 3 significant figures.2 marks
3. A technician prepares a solution of sodium carbonate, Na₂CO₃, by dissolving 6.36 g of the solid in water and making the volume up to exactly 250 cm³ in a volumetric flask. Use relative atomic masses Na 23.0, C 12.0 and O 16.0, and the Avogadro constant, 6.02 × 10²³ mol⁻¹.
   Calculate the concentration of the sodium carbonate solution in mol dm⁻³.3 marks