A chemist runs the reaction indicated by the chemical equation below. At the end of the reaction, he measures a mass of 39.0 g of oxygen. Based on the initial amounts of reagents that he used and on his stoichiometric calculations, 6.21 moles of KOH should have formed in this reaction. Estimate the percent yield of the reaction that the chemist ran. 2 K2O2 (s) + 2 H2O (l) → 4 KOH (s) + O2 (g)