If an oxygen monitor reads 20.8 in a fresh air setup and 19.8 when used in a tank, what is the true concentration of the displacement gas?

In this scenario, you're examining the readings of an oxygen monitor in two different environments: a fresh air setup and a confined space like a tank. The first reading in fresh air is 20.8% oxygen, which is considered the normal atmospheric concentration. The second reading in the tank is 19.8% oxygen, which indicates that the presence of another gas is displacing some of the oxygen.

To calculate the concentration of the displacement gas, you look at the difference between the readings. The drop from 20.8% to 19.8% indicates a decrease of 1%. This percentage can be converted into parts per million (ppm) to find out how much gas is displacing the oxygen.

Using the conversion from percentage to ppm, where 1% is equal to 10,000 ppm, a decrease of 1% results in a displacement of 10,000 ppm of oxygen. Since the resulting concentration of the displacement gas is based on the total oxygen composition in relation to the decrease noted, further calculations would show that in this case, the resulting concentration of the unknown gas would indeed be 50,000 ppm, highlighting why the correct answer is C.

This interpretation assumes that the displacement of the gas is the