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It is now known that dust and other particles can act as heterogeneous catalysts, speeding up the reaction. In the case of an erupting volcano the air would be filled with such particles. So what does sulphur trioxide form when mixed with water? You guessed it, sulphuric acid! Very nasty! SO3 (g) + H2O (l) H2SO4 (aq)
Other gases that could be contributing to the acidity of the lake include hydrogen sulphide (H2S), hydrogen chloride (HCl), hydrogen fluoride (HF). HCl and HF are very strong acids, whilst H2S is a weaker acid, but in a volcanic eruption these three would only found in small quantities. So the lake would indeed be acidic. But how acidic? We’ll come back to this critical point soon. First a bit of theory about aluminium... As our Hollywood Scientists Jonathan Hare and Robert Llewellyn point out, aluminum is a very reactive metal; however, as soon as it is exposed to air, a thin layer of aluminum oxide forms rapidly over the surface. What would happen to this protective oxide layer in the presence of sulphuric acid? The thin oxide layer would react with the acid to form the corresponding aluminium salt and water. Al203(s) + H2SO4(aq) Al2(SO4)3(aq) + H2O
The aluminium metal will further react with the acid...
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