A student collected 35.0 mL of O_2 over water at 25 degree C and a total pressure 745 torr from the decomposition of a 0.2500-g sample known to contain a mixture of KC1 an KCIO_3. The reaction that produced the oxygen was KClO_3 rightarrow 2KCl + 3O_2. How many moles of O_2 were collected? How many grams of KCIO_3 were decomposed? What percentage by mass of the same was 2KCIO_3? (Take H_2O vapor pressure at this temperature to be 23.8 torr).