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ENGR5002 / Week 1 / L1 Introduction
G5GeneratedCurrent spec2:210 marks12 min

Generated, based on Week 1 Exercise 6 and ENGR271 2026 Q3 mixture style

Natural gas in a storage vessel is modelled as an ideal gas mixture of 90% methane (M=16.04 g mol−1M = 16.04\ \mathrm{g\,mol^{-1}}) and 10% ethane (M=30.07 g mol−1M = 30.07\ \mathrm{g\,mol^{-1}}) by mole, at 5.0 bar absolute and 15 deg C. Take R=8.314 J mol−1 K−1R = 8.314\ \mathrm{J\,mol^{-1}\,K^{-1}}.

  1. (a)
    Calculate the average molar mass of the gas.
    [3]
  2. (b)
    Calculate its density using ρ=pM/(RT)\rho = pM/(RT).
    [3]
  3. (c)
    Calculate its relative density (with respect to water) and specific weight.
    [2]
  4. (d)
    Explain why the density of a gas cannot always be treated as constant in hydrostatic calculations, whereas the density of a liquid usually can.
    [2]