What is the mass of water formed during the combustion of 2 liters of propane?

Given:
V (C3H8) = 2 L

To find:
m (H2O) -?

Decision:
1) Write the reaction equation:
C3H8 + 5O2 => 3CO2 + 4H2O;
2) Calculate the molar mass of H2O:
M (H2O) = Mr (H2O) = Ar (H) * N (H) + Ar (O) * N (O) = 1 * 2 + 16 * 1 = 18 g / mol;
3) Calculate the amount of substance C3H8:
n (C3H8) = V (C3H8) / Vm = 2 / 22.4 = 0.09 mol;
4) Determine the amount of substance H2O:
n (H2O) = n (C3H8) * 4 = 0.09 * 4 = 0.36 mol;
5) Calculate the mass of H2O:
m (H2O) = n (H2O) * M (H2O) = 0.36 * 18 = 6.48 g.

Answer: The mass of H2O is 6.48 g.