A sample of a mixture of KClO3 and KBr weighing 7.0950 g is heated in the presence of a small amount of MnO2 which acts as a catalyst of the decomposition reaction 2 KClO3(s) --> 3O2(g) + 2KCl(s) .
The O2(g) is collected in a container over water. The total volume and pressure of the gas in the container was 865.5 mL and 741.5 mm Hg respectively at 27.2oC. The vapour pressure of water at that temperature is 27.1 mm Hg. Assume that all of the KClO3(s) decomposed. What was the %w/w of KClO3(s) in the original mixture?