Chemistry
posted by Billy .
Oxygen gas can be generated by heating KClO3 in the presence of some MnO2.
2KClO3 → 2KCl + 3O2
If all the KClO3 in a mixture containing 1.58 g KClO3 and 0.30 g MnO2 is decomposed, how many liters of O2 gas will be generated at T = 25.0°C and P = 760.6 torr?

I assume that ONLY the KClO3 is decomposing.
mols KClO3 = 1.58/molar mass KClO3.
Using the coefficients in the balanced equation, convert mols KClO3 to mols O2.
Now use PV = nRT, substitute n for mols and the other conditions of the problem and solve for V in liters. Remember T mut be in kelvin and P in atmospheres is R = 0.08206 L*atm/mol*K