Weegy: First balance the equation
C3H8 + 5O2 - - - - - - - > 3CO2 + 4H2O
Convert the mass of C3H8 to moles... [ [ Always work with moles
moles = mass / molar mass
molar mass C3H8 = (3 x 12.01) + (8 x 1.008) = 44.094 g/mol
moles C3H8 = 5.53 g / 44.094 g/mol
= 0.1254 moles C3H8
You need enough moles of O2 to react 0.1254 moles of C3H8, so work out how many moles of O2 are needed to react with 0.1254 moles C3H8.
The balanced equation tells you that
1 mole C3H8 needs 5 moles O2 to fully react
So 0.1254 moles C3H8 needs (5 x 0.1254) moles O2
= 0.6270 moles O2 required to react all the propane.
You need 0.6270 moles of O2
Now use
PV = nRT to determine the volume of O2 at 25 deg C and 1.04 atm that has 0.627 moles of O2
P = pressure (1.04 atm)
V = volume (unknown - Litres)
n = moles (0.627 mol)
T = Temp, must be in Kelvin. Kelvin = deg C + 273.15
so T = 298.15 K (25 deg C = (25 + 273.15 = 298.15 K))
R = gas constant (different for different units of Pressure and volume - see link) For P in atm and Vol in Litres R = 0.0821 L atm K^-1 mol^-1
V = nRT / P
V = (0.627 mol x 298.15 K x 0.0821L atm K^-1 mol^-1) / 1.04 atm
V = 14.8 L (3 sig figs) ] ] (More)

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