# The Combustion of Propane: Calculating the Mass of Oxygen Gas Required

## The Chemical Equation and Molar Mass

The chemical equation below shows the combustion of propane (C3H8):

**C3H8 + 5O2 → 3CO2 + 4H2O**

The molar mass of oxygen gas (O2) is 32.00 g/mol, and the molar mass of C3H8 is 44.1 g/mol.

## Calculating the Mass of Oxygen Gas

What mass of O2, in grams, is required to completely react with 0.025 g C3H8?

The mass of O2 required to completely react with 0.025 g C3H8 is calculated as follows:

**C3H8 + 5O2 = 3CO2 + 4H2O**

Calculate the moles of C3H8: moles = mass / molar mass = 0.025 g / 44.1 g/mol = 5.669 x 10^-4 moles

Using the mole ratio from the reacting equation between C3H8 and O2 (1:5), the moles of O2 = 5 x (5.669 x 10^-4) = 2.83 x 10^-3 moles

Calculate the mass of O2: mass of O2 = moles x molar mass = (2.83 x 10^-3) moles x 32 g/mol = 0.091 g (answer D)

What mass of O2, in grams, is required to completely react with 0.025 g C3H8?

The mass of O2 required to completely react with 0.025 g C3H8 is 0.091 grams.