Thermal decomposition of KHCO3 to KOH ?

[piateczka]

Hi,

Does anyone know if it is possible to thermally decompose KHCO3 to KOH; perhaps it is possible but some specific conditions are required.

I know that KHCO3 decomposes into K2CO3, H2O and CO2 but the question is if it could decompose to KOH?

Thanks!

 

[kenvlach]

No, but that is based upon Gibbs free energies at 25 ^oC; need the values at 100 ^oC (where KHCO₃ decomposes) to be sure. Consider the reaction between possible byproducts:

K2CO3 + H2O(g) + CO2(g) = 2 KOH + 2 CO2(g)

Simplify:

K2CO3 + H2O(g) = 2 KOH + CO2(g)

[Δ]G_{Rxn, 25C} = 2(-378.7) - 394.4 + 1063.5 + 228.6

= +140.3 kJ/mol

Due to positive [Δ]G_{Rxn, 25C}, the reaction won't go.