O-LevelChemistryChemistry of the Environment5070/22 · May/June 2017 · Q910 Marks
Methane, ethane and propane are all gases at room temperature.
- (a)State a use of methane.[1]
- (b)Describe one source of methane in the atmosphere.[1]
- (c)State one possible environmental consequence of the presence of methane in the atmosphere.[1]
- (d)(i)Ethane reacts with chlorine in the presence of ultraviolet light to give a number of different compounds. A 1.00 g sample of one of these compounds contains 0.040 g of hydrogen, 0.242 g of carbon and 0.718 g of chlorine. Calculate the empirical formula of this compound.[2]
- (d)(ii)The relative molecular mass of the compound is 99. Deduce the molecular formula of the compound.[1]
- (e)(i)What is meant by the term diffusion?[1]
- (e)(ii)Explain why propane diffuses faster at 100°C than at 60 °C.[1]
- (e)(iii)Explain why diffusion could be used to separate a mixture of methane and propane.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- B9(a) Fuel
- B9(b) Decomposing vegetation
- B9(c) Climate change / global warming
- B9(d)(i) H: 0.040 / 1 = 0.040 mol C: 0.242 / 12 = 0.020 mol Cl: 0.718 / 35.5 = 0.020 mol (1) Ratio: 2:1:1 (dividing by smallest number of moles) CH₂Cl (1)
- B9(d)(ii) C₂H₄Cl₂
- B9(e)(i) The (overall) movement of particles from high concentration to a low concentration / mixing due to (random) movement of particles
- B9(e)(ii) Particles are moving faster / particles have more kinetic energy
- B9(e)(iii) Molecules/particles have different (relative formula) masses / molecules/particles have different (relative molecular) masses (1) Methane (molecules) move or diffuse faster / butane (molecules) move or diffuse more slowly (1)
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