Answer:
ΔH° = -1815 kJ
Explanation:
The balanced chemical equation
C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l)
tells us that 2220 kJ joules are released in the combustion of one mol propane,C3H8 . So what we need to solve this problem is to find how many moles of propane 20.0 L represent and do the calculation.
To do that, we will be using the Ideal Gas Law since we are told the volume, temperature, and pressure.
PV = nRT ∴ n = PV/RT
P: 1 atm
V: 20.0 L
R= 0.08206 Latm/kmol ( R constant for ideal gases)
T= 25 ºC + 273 = 298 k (Need to convert T to degree Kelvin)
Plugging the values
n = 1 atm x 20.0 L/ (0.08206 Latm/ k mol)
n = 0.82 mol
ΔH° =(-2220 kJ / 1 mol C3H8 ) 0.82 mol C3H8 = -1815 kJ