# Maximizing Usable Air from Decompressing a Scuba Tank

• qwerty1785
In summary, the problem involves finding the amount of usable air from decompressing a standard 80 cu ft scuba tank from 3000psi to 100 psi. The air is being drawn at a rate of 1.5 cubic feet per minute at 20 degrees Celsius. While air is not an ideal gas, the ideal gas law may not work and the van der Waals equation may be needed. The air will become colder and occupy less volume than ideal, but the exact amount is unknown. Using Boyle's law and the fact that one atmosphere equals 14.7 psi, one can find the remaining volume of air in the tank at 100 psi and subtract it from the total capacity of 80 cu ft.
qwerty1785

## Homework Statement

I need to find the amount of usable air from decompressing a scuba tank from 3000psi to 100 psi. The tank is a standart 80cu ft scuba tank and the air is being drawn from the tank at a rate of 1.5 cubic feet per minute and 100 psi at 20 celsius.I know that air is not an ideal gas but am not sure if I can assume it will behave similar here so ideal gas law might not work. would van der waals equation be what I need? I know the air decompressing that much will get very cold and not be as much volume as ideal, but how much is it exactly?

## The Attempt at a Solution

You're going to end up with 80 cubic feet of air when it reaches room temp.

The actual volume of the tank is is .39 cu ft.

If the total volume of room air is 80cu ft, one can figure out the volume of air remaining in the tank at 100 psi. Hint: use Boyles law and the fact one atmosphere=14.7psi

Then subtract this from the entire capacity of 80.

## 1. How does decompressing air affect its behavior?

When air is decompressed, it expands and becomes less dense. This causes a decrease in pressure and an increase in volume. The molecules of air also move farther apart, resulting in a decrease in temperature.

## 2. What causes air to decompress?

Air can be decompressed through various methods, such as opening a valve or reducing the external pressure on a sealed container. It can also occur naturally when air moves from a higher pressure area to a lower pressure area, such as when a balloon is popped.

## 3. How does the behavior of decompressing air differ from compressing air?

While decompressing air causes it to expand and decrease in density, compressing air has the opposite effect. Compressing air reduces its volume and increases its pressure and density. The molecules of air also move closer together, resulting in an increase in temperature.

## 4. What are the practical applications of understanding the behavior of decompressing air?

Understanding the behavior of decompressing air is crucial in various industries, such as aerospace and scuba diving. It is also important in everyday life, such as understanding the effects of altitude changes on air pressure and temperature.

## 5. How can decompressing air be dangerous?

If air is decompressed too quickly, it can cause a condition known as decompression sickness or "the bends." This occurs when nitrogen bubbles form in the bloodstream and can lead to serious health problems. It is important to decompress slowly and safely, especially when diving or traveling to high altitudes.

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