This is how I imagine the process:
- Bottle is full of air at 1 atm
- Bicarbonate and acid are poured in, in proper amount
- Stopper is closed, pressure rises to 2atm
must provide only 1atm in 1.5L, or equivalently, only 0.75L at 2atm, as air provides the rest for free. That is, only 0.06mol CO2
Exegesis by AWK-logists suggests that 1 mol citric acid frees 3 mol CO2
, not 2, because citric acid acts by all its three functions. Less citric acid needed. Hope I grasped it properly, I never needed such a thing for rocket engines.
One 150g mole of tartaric acid frees 2 moles of CO2
. One 192g mole of anhydrous citric acid frees 3 moles of CO2
.Amount of water
: if the acid and the bicarbonate are first dissolved separately, then the solutions poured in the bottle, solubilities apply. A bit excess water helps dissolve.
The presently estimated water amount has no big drawback, does it? It only reduces the buoyancy of the bottle. I suppose it can be seawater
, just try.
Alternately, fine powders of bicarbonate and acid could be mixed dry
, introduced in the bottle, and water be added. This might accept less water, or not, difficult to predict. I don't see clear advantages to this. Maybe the reaction is slower, giving time to close the stopper and get away, useful.
Please take some precautions
before the first trial and during the production. While a soda bottle is not a grenade, I know by experience it makes a strong bang, and among thousand bottles, some will explode. Do it outdoors. Protect your ears. Maybe a scuba mask protects your eyes against debris, and skiing gloves protect your hands, but maybe not, I don't know. I would leave the bottles behind a wall or sandbags immediately after closing the stopper. Use a mirror on a boom to watch if bubbling is finished.