Explanation

The substance used to absorb carbon dioxide gas in combustion analysis is 50% KOH (potassium hydroxide)

50% KOH (potassium hydroxide):

Potassium hydroxide is used to absorb CO (_2) because it reacts with CO (_2) to form potassium carbonate (K(_2 )CO (_3) and potassium bicarbonate (KHCO (_3)).

This makes it an effective absorbent for CO(_2) in combustion analysis.

[ 2KOH + CO_2 rightarrow K_2CO_3 + H_2O ]

 [ KOH + CO_2 rightarrow KHCO_3 ]