[vwyw (OP)]

"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

[lightarrow]

"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

It is correct the first. NaOH reacts with the CO2 present in the air over the solution inside the bottle. 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. With a plastic stopper you can simply unscrew it (not possible to make a glass stopper of that kind).

[vwyw (OP)]

But does the pressure inside the bottle really matters much, does it change that much. []

[eric l]

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.

[Bored chemist]

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.

[lightarrow]

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.

That's right, this must be considered together with what I said and is probably the main reason.

[lightarrow]

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.

I said "tremendous force" not "tremendous pressure", actually, because I had in mind the low pressure combined with a glass stopper "glued" to the bottle by the carbonate (personal experience).

[vwyw (OP)]

I think the glass stopper and the glass bottle stuck together because the is some think form between them, not the pressure problem. But anyway, thanks for lightarrow's help and suggesting a possible but may be not thought of reason.

Anyone, please share your view.

[chris]

Eric has the right answer, the base attacks the glass.

What's the equation for the reaction between sodium hydroxide and glass?

Chris

[eric l]

I never spoke about a chemical reaction, just wrote that the Na₂CO₃ from the reaction of NaOH and CO₂ could combine with the Na₂CO₃component of the glass into big crystals, welding the glass stopper and the glass flask together.

[lightarrow]

What's the equation for the reaction between sodium hydroxide and glass?
Chris

2NaOH + SiO₂ --> Na₂SiO₃ + H₂O.

The solutions of NaOH stored in a glass container must be dilute infact, to avoid this reaction. Better in a plastic container.

[lightarrow]

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.

It's difficult for me to think of "the Na₂CO₃ component of the glass". Glass is a solid solution of SiO₂ and other oxides and/or silicates.

When Na₂CO₃ or other carbonates reacts with SiO₂ at high temperature, it releases CO₂:

Na₂CO₃ + SiO₂ --> Heat --> Na₂SiO₃ + CO₂