[CNR-engineering]

 I cannnot figure this out at all so, I was hoping someone could at least get me started in the right direction, well here goes.

 A student heats a sample of KClO3, KCl, and MnO2 having a mass of 3.6349g. After the reaction is complete, she has collected 346.2ml of Oxygen in a water filled flask. The room tempature and pressure were 23.6 deg C and 763.4 mm Hg respectively. The residue had a mass of 3.1915 grams.
a. What was the partial pressure of oxygen?

b. What volume would the oxygen occupy at STP?

c. What mass of Oxygen was liberated?

d. How many moles of oxygen were produced?

I seriously do not understand this so any help would be nice 

[Borek]

For a you have to check tables of water vapor density. c is the easiest point - where does the mass difference between solids before and after reaction come from?

[CNR-engineering]

So what must I do after I check the table for water density?  I dont understand do I just subtract that from the 763.4mm hg?

[Borek]

Sorry, not water vapor density, but water vapor pressure, something went wrong between brain and fingers  763.4 is a sum of both - oxygen and water partial pressures.