How much CO2 can soda lime absorb?

Question

How much CO2 can soda lime absorb?

Answer 1

Soda lime is actually a mixture of calcium, sodium, and potassium hydroxides with water.  Don't forget that with sodium and potassium, bicarbonate, not carbonate, will be formed, consuming more CO2:

NaOH + CO2 ----> NaHCO3

To find out how much soda lime can absorb, find out how much some mass of each reactant can absorb, then multiply each by the fraction of the reactant present and add to get the final mass of CO2 per some mass of soda lime.

The reactions will be:

Ca(OH)2 + CO2 ----> CaCO3 + H2O

NaOH + CO2 ----> NaHCO3

KOH + CO2 ----> KHCO3

However, the NaOH and KOH are just a few percent of the mixture, and act mostly as catalysts:

NaHCO3 + Ca(OH)2 ----> CaCO3 + NaOH + H2O

See the article for more info.

Answer 2

Assuming that the reaction is 2NaOH + CO2 -> Na2CO3 + H2O, we can figure molecular weights and conclude that 80 grams of NaOH can absorb 44 grams of CO2.