Question

If more than about _____________ percent by volume nitrogen is added to a stichiometric methane-air mixture, the mixture crosses a boundary and enters into the region of flammable mixtures, regardless of the percent by volume of methane or oxygen.

A) 50%
B) 60%
C) 70%
D) 80%

Answer 1

Nitrogen becomes a concern for flammability when it exceeds 60% of the volume in a stoichiometric methane-air mixture, as it can dilute the oxygen and create conditions conducive to combustion.

Step-by-step explanation:

The correct answer is B) 60%. When more than approximately 60% nitrogen by volume is added to a stoichiometric methane-air mixture, the mixture becomes flammable regardless of the methane or oxygen concentration.

This is because nitrogen is an inert gas and does not support combustion; however, it dilutes the oxygen in the air which can then lead to conditions that are favorable for combustion if an ignition source is present.

This is especially relevant when considering the flammability limits of various gas mixes in scenarios such as industrial safety, chemical processing, and fire prevention.