If 8.0 L of ethene gas at STP is completely polymerised to polyethylene, calculate the mass of polyethylene formed. (Molar mass of repeating unit $ceC2H4$ = 28 g mol${}^{-1}$). Assume the polymer contains the same number of repeating units as moles of ethene reacted.

Step-by-step solution

1. Use the molar volume at STP: $V_{\text{STP}}=22.4\mathrm{L},\mathrm{mo}{\mathrm{l}}^{-1}$.
2. Convert the volume of ethene to moles: $n_{ceC2H4}=\frac{8.0\mathrm{L}}{22.4\mathrm{L},\mathrm{mo}{\mathrm{l}}^{-1}}=0.3571\mathrm{mol}$.
3. Since each mole of ethene gives one repeating unit, the number of repeating units equals $0.3571$ mol.
4. Multiply by the molar mass of the repeating unit: $m=0.3571\mathrm{mol}\times 28\mathrm{g},\mathrm{mo}{\mathrm{l}}^{-1}=10.0\mathrm{g}$.
5. Thus the mass of polyethylene produced is $10.0\mathrm{g}$.

Concept tested: Polymerisation of ethene

Published 4 October 2026 · How this solution was prepared and checked