Find the volume of oxygen under normal conditions that you need to take to burn 40 g of methane.

1. Let’s write down the reaction equation:

CH4 + 2O2 = CO2 + 2H2O.

2. Find the amount of methane that has reacted:

n (CH4) = m (CH4) / M (CH4) = 40 g / 16 g / mol = 2.5 mol.

3. According to the reaction equation, we find the amount and then the volume of reacted oxygen (

Vm – molar volume, constant equal to 22.4 l / mol):

n (O2) = n (CH4) * 2 = 2.5 mol * 2 = 5 mol.

V (O2) = n (O2) * Vm = 5 mol * 22.4 L / mol = 112 L.

Answer: V (O2) = 112 liters.