Sciencemadness Discussion Board

How much sodium metal for saturated aqueous NaOH?

m1tanker78 - 31-1-2011 at 03:50

Anybody have a rough estimate? Let's say I want to saturate 250mL of H2O with NaOH. About how much sodium metal would I need to add (not accounting for the bits that explode and eject pieces of Na)?

Tom

ScienceSquirrel - 31-1-2011 at 03:58

Why not use sodium hydroxide pellets or flakes?
This strikes me as a waste of time and money as well as being stupid and dangerous!

Retard-3000 - 31-1-2011 at 04:40

NaOH has a solubility of 1110g per litre at 20C, so to saturate 250ml of water you'd need to dissolve 277.5g NaOH, baring in mind this would take alot of time if you wish to do it safely due to the exothermic nature of the disassociation of NaOH, alot of cooling would also be needed. like ScienceSquirrel said, using sodium metal would be stupid, dangerous and a complete waste.

m1tanker78 - 31-1-2011 at 09:28

So straight Na and NaOH are interchangeable as far as concentrations? 1g of Na in H2O will be the same as 1g of dry NaOH pellets in H2O?

Yes, it's stupid and dangerous and expensive - that's why I'm asking and not doing.

Tom


ScienceSquirrel - 31-1-2011 at 09:42

No, 23g of sodium will react with 18g of water to form 40g of sodium hydroxide and 1g of hydrogen.
So you would have to add 159g of sodium to 375ml of water to get the same effect as dissolving 277.5g of sodium hydroxide in 250ml of water, you would lose about 6.5g of the water as hydrogen gas.