Concentration and gas volumesIB MYP Chemistry: Mind map

Exam questions on Concentration and gas volumes

1. A pharmacist in Lagos prepares a saline solution for a clinic by dissolving 4.5 g of sodium chloride in water and making the solution up to 500 cm³.
   The pharmacist needs 250 cm³ of this solution for a patient. Calculate the mass of sodium chloride in 250 cm³ of the solution.2 marks
2. A student in Singapore reacts magnesium ribbon with excess dilute hydrochloric acid at room temperature and pressure. The equation is Mg + 2HCl → MgCl₂ + H₂. At room temperature and pressure, one mole of any gas occupies 24 dm³. The relative atomic mass of magnesium is 24.
   Calculate the volume of hydrogen, in cm³, produced when all of the 0.60 g of magnesium reacts.2 marks
3. A quality-control chemist at a food factory in Seville checks the concentration of a sodium hydroxide cleaning solution by titration. She measures 25.0 cm³ of the cleaning solution into a conical flask and adds hydrochloric acid of concentration 0.100 mol dm⁻³ from a burette until the indicator changes colour. The mean titre is 20.0 cm³. The equation is NaOH + HCl → NaCl + H₂O.
   Calculate the number of moles of hydrochloric acid used in the titration.3 marks