In: Chemistry
When propane is burned, the balanced reaction is: C3H8(l) + 5 O2(g) -> 3 CO2(g) + 4 H2O(g). If 31.66 L of water vapor are produced at 865.7 torr and 75°C, how many grams of propane were burned?
The reaction:
C3H8(l) + 5 O2(g) -> 3 CO2(g) + 4 H2O(g).
is already balanced
so
relate mol of water to mol of propane
mol of water = from ideal gas law
Assume Pressure is pressure of GAS and not of device
so
Pgas = 865.7 torr
R = 62.4 tottL/molK
T = 75°C = 75+273 K = 348 K
V = 31.66 L
Apply Ideal Gas Law,
PV = nRT
where
P = absolute pressure
V = total volume of gas
n = moles of gas
T = absolute Temperature
R = ideal gas constant
n = PV/(RT)
n = (865.7*31.66)/(62.4*348)
n = 1.262
1 mol of propane = 4 mol of water
x mol of propane = 1.262 mol of water
x = 1.262/4 = 0.3155 mol of propane
mass= mol*MW = 0.3155*44.10 = 13.91355 g of propane must be burnt