Small quantities of oxygen gas are sometimes generated by heating KClO3 in the presence of MnO2 as a c

Question

2KClO3(s) → 2KCl(s) + 3O2(g)



What volume (ml) of O2 is collected over water at 22.0 oC by the reaction of 0.274 g of KClO3 if the barometric pressure is 726.2 mm Hg
The vapor pressure of water at 22.0 oC is 19.8 mm Hg.

Answer 1

The MW of KClO3 is 122.55 (ref.), so 0.274 g KClO3 is .0022358 M. This will evolve 3/2 * .0022358 = .0033537 M O2 * 22.4 L/M = .075124 L O2 at STP. Correcting for temperature, pressure and partial pressure H2O, multiply by 295/273 * 760 / (726.2 -19.8) and volume at given temp. and press. = 0.087337 L.