Determine the amount of oxygen needed to burn 12 grams of methane?

Given:
m (CH4) = 1.6 g
To find:
V (O2) =?
Solution:
1) Let’s compose the equation of the chemical reaction, let the volume of oxygen be x l.
CH4 + 2O2 = CO2 + 2H2O
2) Find the molecular weight of methane.
M (CH4) = 12 + (1 x 4) = 16 g / mol
3) Find the molar volume of oxygen.
Vm (O2) = 22.4 x 2 = 44.8 g / mol
4) 1.6 g: 16 g / mol = x L: 44.8 L / mol
x = (1.6 x 44.8): 16 = 4.48 liters.
Answer: V (O2) = 4.48 liters.