What is the volume of air required to completely burn 50 liters of methane?

Given:
V (CH4) = 50 l

To find:
V (air) -?

Solution:
1) Write the equation of a chemical reaction:
CH4 + 2O2 => CO2 + 2H2O;
2) Based on the Gay-Lussac law (the law of volumetric ratios), it is necessary to draw up a proportion and solve it:
1 L CH4 – 2 L O2;
50 L CH4 – x L O2;
V (O2) = x = 50 * 2/1 = 100 l;
3) Calculate the air volume (under normal conditions):
V (air) = V (O2) * 100% / φ (O2) = 100 * 100% / 21% = 476 HP

Answer: The air volume is 476 liters.