In combustion analysis, 50% KOH (potassium hydroxide) solution is commonly used rather than 100% KOH. The reason behind this choice is related to the absorbent properties and practical considerations. Here's why:
Absorbent properties: The purpose of KOH in combustion analysis is to absorb carbon dioxide (CO2) produced during combustion. KOH is a strong base and reacts with CO2 to form potassium carbonate (K2CO3). However, the reaction between KOH and CO2 is exothermic, meaning it releases heat. Using 100% KOH solution would lead to a highly exothermic reaction, potentially causing an increase in temperature and affecting the accuracy of the analysis. By diluting KOH to a 50% solution, the exothermic reaction is moderated, minimizing any potential temperature changes and ensuring more accurate measurements.
Practical considerations: Working with a 50% KOH solution instead of 100% KOH also offers practical advantages. 50% KOH is more viscous than the concentrated solution, making it easier to handle and transfer. Additionally, the dilution helps reduce the risk of splattering or boiling during the reaction, which can be hazardous. It allows for better control and safer handling during the combustion process.
It's worth noting that the specific concentration of KOH used in combustion analysis can vary depending on the laboratory or procedure. While 50% KOH is commonly used, other concentrations may also be employed based on the specific requirements of the analysis and the equipment being used.