Gas volumes and molar volumeEdexcel A-Level Chemistry: Mind map

Exam questions on Gas volumes and molar volume

1. A technician reacts marble chips (calcium carbonate) with an excess of dilute hydrochloric acid and collects the carbon dioxide produced in a large gas syringe. Everything is measured at room temperature and pressure (rtp), where the molar volume of any gas is 24.0 dm³ mol⁻¹.
   Calculate the mass of calcium carbonate (M = 100.1 g mol⁻¹) needed to produce 90.0 cm³ of carbon dioxide at rtp.2 marks
2. A student studies the complete combustion of gaseous hydrocarbons in a eudiometer (a graduated gas-measuring tube). All gas volumes are measured at the same temperature and pressure, and any water formed condenses to a liquid whose volume can be ignored.
   25 cm³ of ethene, C₂H₄, is burned in 100 cm³ of oxygen. The equation is C₂H₄(g) + 3O₂(g) → 2CO₂(g) + 2H₂O(l). Calculate the total volume of gas remaining when the mixture returns to the original temperature and pressure.2 marks
3. Car airbags are inflated by the rapid decomposition of sodium azide, NaN₃, in a gas generator: 2NaN₃(s) → 2Na(s) + 3N₂(g). Take the molar volume of gas as 24.0 dm³ mol⁻¹ at room temperature and pressure and the relative formula mass of NaN₃ as 65.0.
   An airbag must be inflated with 60.0 dm³ of nitrogen at rtp. Calculate the mass of sodium azide needed.3 marks