Question

How many liters of water vapor can be produced if 8.9 liters of methane has (CH4) are combusted, if all measurements are taken at the same temperature and pressure? Please answer & explain

Answer 1

You can do this the long way or the short way. The long way is
1. Write the equation and balance it.
2. Convert L CH4 to mols CH4 using PV = nRT.
3. Using the coefficients in the balanced equation, convert mols CH4 to mols H2O vapor.
4. Using PV = nRT convert mols H2O vapor to volume.

The short way:
1. Write and balance the equation.
CH4 + 2O2 ==> CO2 + 2H2O

2. Use L directly with the coefficients in the balanced equation. As long as the equation deals with gases and there is no P or T difference between start and finish, there is no need to go through the middle steps.
8.4 L CH4 x (2 mols H2O/1 mol CH4) = 8.4 x 2 = 16.8 L H2O vapor.