Boiling Soda Reaction - Does It work? [closed]








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I've come across a series of reactions, where $$\ce{2NaHCO3 <=> Na2CO3 + H2O + CO2}$$ at temperatures above 50 degrees Celsius, and $$\ce{Na2CO3 + H2O <=> NaHCO3 + NaOH}$$ I Have 3 questions about these equations:


1. Will the above reactions proceed in a boiling Baking Soda solution set to reflux until virtually all of the baking soda is converted to lye and CO2?
2. If so, would the reaction follow a half-life pattern, over a certain period of time?
3. How would I calculate the amount of time required to convert a saturated baking soda solution into a solution with a certain concentration of lye?


I appreciate any advice provided.




Actually, if one adds your two reactions:


$\ce{2 NaHCO3 <=> Na2CO3 + H2O + CO2}$


$\ce{Na2CO3 + H2O <=> NaHCO3 + NaOH}$


Upon cancelling, to derive the reaction:


$\ce{ NaHCO3 <=> NaOH + CO2}$


which implies that heated Sodium bicarbonate is a chemically active source of Lye, if one allows the CO2 gas to escape (which answers (a) of your question).


To answer (b) and (c), add Aluminum to the heated aqueous mix and it will dissolve, and you could collect the generated hydrogen gas over water and record volume increase over time. Reaction:


$\ce{2 Al + 6 NaOH -> 2 Al(OH)3 + 3 H2 (g)}$


Now, per this [Aluminum shiny finish destroyed in dishwasher](https://www.finishing.com/410/66.shtml), you have an understanding as to why this occurs with Aluminum ware in the presence of NaHCO3, which is a popular spotless-rinse agent employed in dishwasher's washing powder.


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2NaHCO3 --> Na2CO3+H2O+CO2 at temperatures above 50 degrees Celsius: TRUE. 


However, Na2CO3+H2O --> NaHCO3+NaOH is a hydrolysis reaction: it only goes to a small extent, maybe 2-5%, and on evaporating the water, it goes back to Na2CO3. Na2CO3 melts at 851C without decomposition.


So, if you take a solution of NaHCO3 (pH ~8.5) and boil it, you will generate a solution of Na2CO3 (pH ~12) by loss of CO2 and if you keep evaporating the water, you will get Na2CO3 as a crystalline powder (and when it cools, it will begin absorbing water from the air to form one or more of its many hydrates).


 -2