Question

We have purchased an oxygen analyzer that is calibrated with pure nitrogen and pure oxygen. It measures 20.91% when it samples air in the atmosphere. The analyzer is reading in %volume.

We have built a container that allows gas to escape. It is initially filled with air. The container is about 6 cu.ft and we have about 4 inch diameter hole with a mechanism to close and open the hole. The oxygen analyzer is on the other side of the room which the gas mixture unit is isolated in the explosive room designed to withstand explosion. We then introduce propane into the system. As more propane we have introduced into the container, the oxygen decreases to 20.14%.

We want to use the measurement of oxygen to calculate the air-fuel ratio. The combustion reaction is:

C₃H₈+5O₂⟶3CO₂+4H₂O,

so a stoichiometric air-fuel mixture should have 1 part propane and 5 parts pure oxygen, or 1 part propane and 25 parts air, approximately (by volume).

Does the nitrogen-to-oxygen ratio remain constant (79/21=3.76) when propane is introduced in the container and partially displaces the air?

Answer 1

No, the nitrogen-to-oxygen ratio does not remain constant when propane is introduced and partially displaces the air. The ratio of nitrogen to oxygen in air is approximately 79/21, but when propane is introduced, the ratio changes because propane is not comprised of nitrogen and oxygen.

Step-by-step explanation:

No, the nitrogen-to-oxygen ratio does not remain constant when propane is introduced and partially displaces the air. The ratio of nitrogen to oxygen in air is approximately 79/21, but when propane is introduced, the ratio changes because propane is not comprised of nitrogen and oxygen.

The combustion reaction of propane with oxygen produces carbon dioxide and water, which means the levels of nitrogen and oxygen decrease in the container.

To calculate the air-fuel ratio, we need to know the composition of the gas mixture. In this case, the propane introduced into the container will displace both nitrogen and oxygen in the air, changing the nitrogen-to-oxygen ratio.