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"Why is NaOH(aq) stored in glass reagent bottle with a plastic stopper?"This is a question from my school exam?The given answer is that NaOH reacts with CO2 to form Na2CO3 and is a glass stopper is used, the glass stopper will get stuck tightly. By the reaction 2NaOH(aq) + CO2(g) -> Na2CO3(s) + H2O(l). But is this correct? Or is it the reaction between NaOH with SiO2? 2OH- + SiO2 -> SiO3- + H2O
One reason is that Na2CO3 is also a component of glass. So the Na2CO3 formed by the reaction of NaOH and CO2 in the air can start crystallizing on the Na2CO3 in the glass, thus creating a bonding between stopper and bottle.There are Teflon sleeves for standardized conical glass stoppers that prevent this, and there are also conical plastic stoppers. You do not need to use a screw stopper.
Eric has the right answer, the base attacks the glass.As for "A glass stopper has a conical shape and to remove it with low pressure inside you should make a tremendous force (breaking it or the bottle) to pull it out. "As far as I can see the "temendous pressure" would be roughly 300 millionths of an atmosphere, a lot less than day to day variation in atmospheric pressure.
Eric has the right answer, the base attacks the glass.
What's the equation for the reaction between sodium hydroxide and glass?Chris
I never spoke about a chemical reaction, just wrote that the Na2CO3 from the reaction of NaOH and CO2 could combine with the Na2CO3 component of the glass into big crystals, welding the glass stopper and the glass flask together.