Ethene (C₂H₄) polymerises to polyethylene according to the simplified equation n C₂H₄ → (C₂H₄)ₙ. If 6.0 L of ethene at NTP is completely polymerised, calculate the mass of polyethylene formed, assuming the polymer contains the same number of repeating units as moles of ethene reacted. Molar mass of repeating unit C₂H₄ = 28 g mol⁻¹. Assume 1 mol gas = 22.4 L.
Answer
7.5 g
The correct answer is 7.5 g — Mass of polyethylene: 0.2679 mol × 28 g mol⁻¹ = 7.5 g.
Step-by-step solution
- Find moles of ethene: 6.0 L ÷ 22.4 L mol⁻¹ = 0.2679 mol.
- Each mole of ethene gives one repeating unit of polyethylene.
- Mass of polyethylene: 0.2679 mol × 28 g mol⁻¹ = 7.5 g.
Common mistake: Not converting volume to moles before multiplying by molar mass
Concept tested: Polymerisation stoichiometry
Published · How this solution was prepared and checked
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