Can acids corrode glass containers?

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Can acids corrode glass containers?
« on: 26/11/2011 12:01:02 »
Susan asked the Naked Scientists:
Why won't most acids corrode glass containers?

What do you think?
« Last Edit: 26/11/2011 12:01:02 by _system »


Offline lightarrow

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Can acids corrode glass containers?
« Reply #1 on: 26/11/2011 12:55:36 »
Because those which do corrode glass, as HF, are toxic and make toxic gases in the reaction, so are not used.
About the other strong acids, as HCl, H2SO4 ecc. they don't attack glass, even if it is essentially an oxide, that is silicon dioxide, because this is a covalent compound with strong bonds and because the resultant Si4+ ion of the hypotetical reaction is a too strong lewis acid to form in presence of water, so it would immediately react with the water formed, re-generating the initial acid and the silicon dioxide.

IF this reaction happened:

4H+ + SiO2 → 2H2O + Si4+,

then immediately the reverse would happen:

2H2O + Si4+ → 4H+ + SiO2
and this would be much more favourite.

In conclusion, the equilibrium:

4H+ + SiO2 ↔ 2H2O + Si4+

is strongly displaced to the left.

HF acts with a different mechanism, because it forms SiF4 and H2SiF6 which are stable, covalent compounds, so no Si4+ ions are formed.
« Last Edit: 26/11/2011 13:15:36 by lightarrow »