Gas volumes and the ideal gas equationEdexcel International A Level Chemistry: Mind map

Exam questions on Gas volumes and the ideal gas equation

1. A student reacts 0.120 g of magnesium ribbon with an excess of dilute hydrochloric acid and collects the hydrogen in a gas syringe at room temperature and pressure (rtp). The molar volume of a gas at rtp is 24.0 dm³ mol⁻¹. The relative atomic mass of magnesium is 24.3.
   The student collects only 108 cm³ of hydrogen. Suggest two reasons why the measured volume is less than the calculated volume.2 marks
2. A gas cylinder of fixed volume 2.50 dm³ contains 4.00 g of methane, CH₄ (molar mass 16.0 g mol⁻¹), at 300 K. Take R = 8.31 J K⁻¹ mol⁻¹ and the molar volume at rtp as 24.0 dm³ mol⁻¹.
   Calculate the volume the methane would occupy at rtp and use this to state whether the gas in the cylinder is at a higher or lower pressure than atmospheric pressure.2 marks
3. A volatile liquid X is one of propanone (C₃H₆O), diethyl ether (C₄H₁₀O) or hexane (C₆H₁₄). A sample of mass 0.205 g is vaporised completely in a gas syringe and occupies 85.0 cm³ at 373 K and a pressure of 101 kPa. Take R = 8.31 J K⁻¹ mol⁻¹. Relative atomic masses: H = 1.0, C = 12.0, O = 16.0.
   Calculate the amount, in mol, of X in the gas syringe.3 marks