Chemistry · May / June 2026 · Paper 12 · Question 1

The melting and boiling points of four substances are shown. | | melting point /°C | boiling point /°C | |---|---|---| | ammonia, NH3 | –78 | –33 | | hydrogen sulfide, H2S | –85 | –61 | | propane, C3H8 | –190 | –42 | | xenon, Xe | –112 | –107 | Which substance has the greatest rate of diffusion at –50°C?

1. Aammonia
2. Bhydrogen sulfide
3. Cpropane
4. Dxenon

As printed in the paper