Sciencemadness Discussion Board

Sodium Hydroxide

awlb2 - 29-12-2016 at 12:40

If anyone is able to help me with a question I have I would be very grateful. I have a dilute solution (approx. 3moldm/3) of NaOH in water, I would like to know if the water could be evaporated without significant losses as Na2CO3? For example if a small amount (E.g. a single drop) was left for some time(at room temp.), until all water evaporates would it still contain significant amounts of NaOH. What if the solution was boiled to dryness?

Many thanks in advance!

[Edited on 29-12-2016 by awlb2]

brubei - 29-12-2016 at 14:45

Sodium hydroxyde exposed to atmospheric CO2 slowly gives hydrogenocarbonate :
NaOH + CO2 <<<=> NaHCO3
This result in a light loss of basicity strenght but the équilibrium is reversible and your NaOH is recovered as you will evaporate it to dryness.

[Edited on 29-12-2016 by brubei]

macckone - 29-12-2016 at 16:50

Sodium hydroxide will not go to dryness without heat.
Almost 10% is converted to carbonate in commercial operation.

unionised - 30-12-2016 at 07:44

Quote: Originally posted by brubei  
Sodium hydroxyde exposed to atmospheric CO2 slowly gives hydrogenocarbonate :
NaOH + CO2 <<<=> NaHCO3
This result in a light loss of basicity strenght but the équilibrium is reversible and your NaOH is recovered as you will evaporate it to dryness.

[Edited on 29-12-2016 by brubei]

MAinly wrong.
The product of leaving NaOH exposed to air is initially the carbonate and eventually (so I'm told; I never waited that long) the sesquicarbonate.

Boiling down a solution to dryness will not give you NaOH.

awlb2 - 30-12-2016 at 13:23

Thanks everybody, my NaOH is still useful as a solution nonetheless.

Happy New Year Everyone!

AJKOER - 2-1-2017 at 04:05

Heat while connected to an even bad working vacuum pump to your NaOH/H2O solution.

It should boil faster absent the presence of CO2 and air.

Not commercial path due to cost.