why is only 20% of freshly prepared KOH solution used in the expirement??

Dear student,
Please find below the solution to the asked query. 

KOH should be prepared freshly or else it can react with carbon dioxide, forming potassium carbonate and water.
As a result of which experiment will not lead proper results.

2KOH + CO2 -------> K2CO3 + H2O​


Only 20 % of KOH is used because it is the optimum concentration of KOH which is required for the experiment.

Hope this information will clear your doubts about the topic. 
If you have any more doubts just ask here on the forum and our experts will try to help you out as soon as possible. 
Regards.  
 

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