The chemical reaction is expressed as:
4KO2+2CO2→2K2CO3+3O2
We are given the amount of KO2 to be used in the reaction. This will be the starting point of our calculations. We do as follows:
0.425 mol KO2 ( 3 mol O2 / 4 mol KO2 ) = 0.319 mol O2 produced
Hope this answers the question. Have a nice day.