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How come acids never melt the glass beakers theyre in?
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Jay T Arnott
How come acids never melt the glass beakers theyre in?
Glass is largely impervious to the common mineral acids, with the exception of HF (hydrofluoric acid).
This is actually in chemical terms a weak acid because it does not fully dissociate into H+ and F- in water. What it is, however, is an extremely corrosive acid. (So don’t confuse acid “strength” with the corrosion ability).
But HF does not “dissolve” glass. It reacts with it.
SiO2 (glass) + 4 HF ===> SiF4 + 2H2O
The actual progress of this reaction is complex (it’s to do with which ions in the HF bind to the surface etc) but the general thrust is that you’re turning your lovely tough glass into SiF4 which is a gas and is toxic.
You also release a lot of heat.
DHr= DHp - DHr
DHr = -2185 - (-2002) = -185 kJ/mol
So for each gram of glass you dissolve, you release 3 kilojoules of heat and 400 mL of toxic gas. That’s enough heat to flash boil a mL of water.
Glass is largely impervious to the common mineral acids, with the exception of HF (hydrofluoric acid).
This is actually in chemical terms a weak acid because it does not fully dissociate into H+ and F- in water. What it is, however, is an extremely corrosive acid. (So don’t confuse acid “strength” with the corrosion ability).
But HF does not “dissolve” glass. It reacts with it.
SiO2 (glass) + 4 HF ===> SiF4 + 2H2O
The actual progress of this reaction is complex (it’s to do with which ions in the HF bind to the surface etc) but the general thrust is that you’re turning your lovely tough glass into SiF4 which is a gas and is toxic.
You also release a lot of heat.
DHr= DHp - DHr
DHr = -2185 - (-2002) = -185 kJ/mol
So for each gram of glass you dissolve, you release 3 kilojoules of heat and 400 mL of toxic gas. That’s enough heat to flash boil a mL of water.
Glass, as a rule, is more vulnerable to bases than acids. There is one exceedingly evil material, chlorine trifluoride Sand Won't Save You This Time that reacts with absolutely everything. In the words of John Clark:
It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively.
Glass, as a rule, is more vulnerable to bases than acids. There is one exceedingly evil material, chlorine trifluoride Sand Won't Save You This Time that reacts with absolutely everything. In the words of John Clark:
It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively.
Glass is largely impervious to the common mineral acids, with the exception of HF (hydrofluoric acid).
This is actually in chemical terms a weak acid because it does not fully dissociate into H+ and F- in water. What it is, however, is an extremely corrosive acid. (So don’t confuse acid “strength” with the corrosion ability).
But HF does not “dissolve” glass. It reacts with it.
SiO2 (glass) + 4 HF ===> SiF4 + 2H2O
The actual progress of this reaction is complex (it’s to do with which ions in the HF bind to the surface etc) but the general thrust is that you’re turning your lovely tough glass into SiF4 which is a gas and is toxic.
You also release a lot of heat.
DHr= DHp - DHr
DHr = -2185 - (-2002) = -185 kJ/mol
So for each gram of glass you dissolve, you release 3 kilojoules of heat and 400 mL of toxic gas. That’s enough heat to flash boil a mL of water.
Glass is largely impervious to the common mineral acids, with the exception of HF (hydrofluoric acid).
This is actually in chemical terms a weak acid because it does not fully dissociate into H+ and F- in water. What it is, however, is an extremely corrosive acid. (So don’t confuse acid “strength” with the corrosion ability).
But HF does not “dissolve” glass. It reacts with it.
SiO2 (glass) + 4 HF ===> SiF4 + 2H2O
The actual progress of this reaction is complex (it’s to do with which ions in the HF bind to the surface etc) but the general thrust is that you’re turning your lovely tough glass into SiF4 which is a gas and is toxic.
You also release a lot of heat.
DHr= DHp - DHr
DHr = -2185 - (-2002) = -185 kJ/mol
So for each gram of glass you dissolve, you release 3 kilojoules of heat and 400 mL of toxic gas. That’s enough heat to flash boil a mL of water.
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Glass, as a rule, is more vulnerable to bases than acids. There is one exceedingly evil material, chlorine trifluoride Sand Won't Save You This Time that reacts with absolutely everything. In the words of John Clark:
Glass, as a rule, is more vulnerable to bases than acids. There is one exceedingly evil material, chlorine trifluoride Sand Won't Save You This Time that reacts with absolutely everything. In the words of John Clark:
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