Gas volumes and molar volumeEdexcel A-Level Chemistry: Flashcards
What these 12 flashcards ask
- What is the molar volume of any gas at rtp?
- State Avogadro's law.
- How do you find the amount of gas, in mol, from a volume in cm³ at rtp?
- When can the coefficients in an equation be used directly as a volume ratio?
- Why is liquid water ignored in combustion volume calculations?
- 10 cm³ of CH₄ burns completely in excess oxygen. What volume of CO₂ forms?
- What volume of oxygen is needed to burn 20 cm³ of propane (C₃H₈)?
- Method to find the volume of hydrogen from a known mass of magnesium?
- In Core practical 1, why is the acid in excess?
- Name the apparatus used to collect hydrogen in Core practical 1.
- Give one reason the measured molar volume in Core practical 1 may be too low.
- Why may the measured molar volume be too high?
Exam questions on Gas volumes and molar volume
- 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
- 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
- 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
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).