Chemical of the Week 10 – Hydrogen Sulfide

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This week’s molecule came about because of an interesting conversation at a BBQ (thanks Gareth !). Hydrogen sulfide has been in the news recently as it can act as a superconductor at approximately 200K (-70 oC). Superconductors conduct electricity with zero resistance and also expel magnetic fields (Meissner effect) below a critical temperature. The ultimate goal would be to have a superconductor operating at room temperature resulting in huge efficiency savings when generating electricity. It seems that under high pressure (about 100 million times atmospheric pressure, created by pushing two diamond bits together) the H2S solidifies and is converted into H3S. The presence of hydrogen atoms in the compound is beneficial as hydrogen oscillates at the highest frequency of any atom. The researchers are now turning to other hydrogen rich molecules to try and increase the operating temperature even more.

Hydrogen sulfide is a colourless gas at room temperature but definitely not odourless. It’s the smell we love to hate, the smell of the stink bomb, rotten eggs. Sulfur and sulfur oxides don’t have a specific smell but reduce sulfur and all that changes. Organic molecules containing sulfur are renowned for being smelly. There is a great poster by compound interest showing all the smelly sulfur containing body odours.

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Hydrogen sulfide has to be handled with care as exposure to high concentrations of the gas can be fatal and it has been reported in some clusters of suicides. The town of Rotorua in New Zealand is famed for its geothermal hot springs and the associated rotten egg smell. As its population has had a low level exposure to hydrogen sulfide the World Health Organisation has issued a study on long term health effects of exposure.

Hydrogen sulfide is an important chemical on the AS syllabus, as we meet the group VI hydrides when discussing hydrogen bonding, we look at the shape of the hydrogen sulfide molecule (an analogue to the water molecule) and it’s also an example of the various oxidation states we can find sulfur in. It may not be as interesting as water but I think it gives it a run for its money !

p.s who grew up with hydrogen sulphide ?

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